Try:
– If you have access to your Dashboard’s Plugins page, try 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: https://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).
Iif 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 you can install plugins, install 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.
