File Upload Limit

The maximum upload size is controlled at the server-level, not by WordPress. Here are three ways you can increase the upload limit:
1. If you can edit or override the system `php.ini` file, increase the maximum file and post sizes. For example, `upload_max_filesize = 100M ;` and `post_max_size = 100M ;`
2. If you cannot edit or override the system `php.ini` file, add `php_value upload_max_filesize 100M` and `php_value post_max_size = 100M` to your `.htaccess` file.
3. If neither of these work, it’s time to ask your hosting provider to increase the maximum file and post sizes on your account. Keep in mind that most decent hosting providers allow this, and If your hosting provider won’t accommodate you, perhaps it’s time to find a new hosting provider.
4. There are some plugins in the plugin directory that can help you get around this limit, for instance, helping you “chunk” your uploads, breaking them into smaller parts. Try searching “increase file upload limit”.
(in the above examples, the limit is set to 100MB)

Error 500: Internal Server Error

Internal server errors (error 500) are often caused by plugin or theme function conflicts, so if you have access to your admin panel, try deactivating all plugins. If you don’t have access to your admin panel, try manually resetting your plugins (no Dashboard access required). If that resolves the issue, reactivate each one individually until you find the cause.
If that does not resolve the issue, try switching to the default theme for your version of WordPress to rule-out a theme-specific issue. If you don’t have access to your admin panel, access your server via SFTP or FTP, or a file manager in your hosting account’s control panel, navigate to `/wp-content/themes/` and rename the directory of your currently active theme. This will force the default theme to activate and hopefully rule-out a theme-specific issue.
If that does not resolve the issue, it’s possible that a `.htaccess` rule could be the source of the problem. To check for this, access your server via SFTP or FTP, or a file manager in your hosting account’s control panel, and rename the `.htaccess` file. If you can’t find a `.htaccess` file, make sure that you have set your SFTP or FTP client to view invisible files.
If you weren’t able to resolve the issue by either resetting your plugins and theme or renaming your .htaccess file, we may be able to help, but we’ll need a more detailed error message. Internal server errors are usually described in more detail in the server error log. If you have access to your server error log, generate the error again, note the date and time, then immediately check your server error log for any errors that occurred during that time period. If you don’t have access to your server error log, ask your hosting provider to look for you.

Out of Memory Errors

If you’re seeing this error either suddenly (no specific task was done to cause the error) or frequently, try deactivating all plugins to rule-out a plugin-specific issue and try switching themes to rule-out a theme-specific issue.
Otherwise, here are three ways to increase PHP’s memory allocation:
1. If you can edit or override the system `php.ini` file, increase the memory limit. For example, `memory_limit = 128M`
2. If you cannot edit or override the system `php.ini` file, add `php_value memory_limit 128M` to your `.htaccess` file.
3. If neither of these work, it’s time to ask your hosting provider to temporarily increase PHP’s memory allocation on your account.
(in the above examples, the limit is set to 128MB)

Error Related to Missing or Damaged Core Files

Try downloading WordPress again, access your server via SFTP or FTP, or a file manager in your hosting account’s control panel, and delete then replace your copies of everything except the `wp-config.php` file and the `/wp-content/` directory with fresh copies from the download. This will effectively replace all of your core files without damaging your content and settings.
Some uploaders tend to be unreliable when overwriting files, so don’t forget to delete the original files before replacing them.

Deactivating ALL (yes all) plugins temporarily

– deactivating ALL (yes all) plugins temporarily to see if this resolves the problem (plugin functions can interfere). If this works, re-activate them individually (one-by-one) to find the problematic plugin(s).
– If you don’t have access to your Dashboard’s Plugins page, try manually resetting your plugins (no Dashboard access required). Here is another tutorial: http://www.wpbeginner.com/plugins/how-to-deactivate-all-plugins-when-not-able-to-access-wp-admin/ – If that resolves the issue, reactivate each one individually until you find the cause. Also remember to deactivate any plugins in the mu-plugins folder (if you have created such folder). The easiest way is to rename that folder to mu-plugins-old.
– switching to the unedited default Theme (Twenty Seventeen, etc.) for a moment using the WP dashboard to rule out any theme-specific issue (theme functions can interfere like plugins).
If you don’t have access to your Dashboard’s Appearance page, access your server via FTP/ SFTP , or a file manager in your hosting account’s control panel (consult your hosting provider’s documentation for specifics on these), navigate to /wp-content/themes/ and switch to the default theme by renaming your current theme’s folder by adding “-old” to the end of the folder name. Alternately, you can remove other themes except the default theme (Twenty Seventeen, etc.). That will force your site to use it.
– If the above steps don’t resole the issue, try MANUALLY updating. Download WordPress again and unzip it. Access your server via SFTP or FTP, or a file manager in your hosting account’s control panel (consult your hosting provider’s documentation for specifics on these), and delete then replace your copies of everything on the server except the wp-config.php file and the /wp-content/ directory with fresh copies from the download. This will effectively replace all of your core files without damaging your content and settings. Please read the Manual Update directions first.

Error Related to Plugin or Theme Conflict

This may be a plugin or theme conflict. Please attempt to disable all plugins, and use one of the default (Twenty*) themes. If the problem goes away, enable them one by one to identify the source of your troubles.
If you can install plugins, install “Health Check”: https://wordpress.org/plugins/health-check/ On the troubleshooting tab, you can click the button to disable all plugins and change the theme for you, while you’re still logged in, without affecting normal visitors to your site.

Cannot Access Dashboard

Try manually resetting your plugins (no Dashboard access required). If that resolves the issue, reactivate each one individually until you find the cause.
If that does not resolve the issue, access your server via SFTP or FTP, or a file manager in your hosting account’s control panel, navigate to `/wp-content/themes/` and rename the directory of your currently active theme. This will force the default theme to activate and hopefully rule-out a theme-specific issue (theme functions can interfere like plugins).