– 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).
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 resolve 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.