Can’t See Backend

Have you tried:
– Flushing any caching plugins you might be running, as well as server and/or browser caches. Not just your browser, but any op cache or content network cache as well such as Cloudflare. If your host provider has a “Purge Varnish” option or if you can ask your provider to flush memcache on your server.
– If that does not resolve the issue, 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 that does not resolve the issue, or if you can’t get into your admin dashboard, try resetting the plugins folder by FTP. Sometimes, an apparently inactive plugin can still cause problems. 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.
– If that does not resolve the issue, keep all plugins deactivated and try switching to the unedited default Theme (Twenty Seventeen) 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 admin area, use FTP , or your web-host’s cPanel or whatever file management application your host provides (no Dashboard access required). 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. That will force your site to use it.
– If all the above steps do not resolve the issue, then try MANUALLY updating. Download a fresh copy of the WordPress .zip file to your computer, unzip it, and use that to copy up all files and folders EXCEPT the wp-config.php file and the /wp-content/ directory. You may need to delete the old wp-admin and wp-includes folders and files on your server before uploading the new ones. Please read the Manual Update directions first.
– Backup: If you haven’t already done, always backup everything (including your database) before doing any actions, just in case something really goes wrong. You can never have enough backups!