Provided you have the option to make a backup and in case of need fully restore this backup, and perform that backup, for both the files and the database, and in addition quickly download to disk a copy of the plugins and themes directories, I would suggest you try a forceful reinstallation of wordpress, with its latest version.
It would mean taking the wordpress zip archive from ww.wp.xz.cn, removing the wp-admin, wp-includes, wp-content directories from your hosting (I mentioned backups, right?), and uploading the contents of the wordpress zip archive to your hosting, accepting to overwrite the php files at the site’s root.
Attempting to load your blog afterwards would cause a database upgrade (I am certain I mentioned backups) and a reset of everything that regards plugins and themes, plus it would make the blog work with the latest wordpress version.
Hopefully, it should work to fix whatever problem you have.
Now, if the blog NEEDS its old contents, such as themes or plugins, they would have to be restored, one by one, to see if suddenly the error 500 is back (and then we have a culprit, and know it’s that one that needs fixing.)
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This reply was modified 6 years, 2 months ago by
Sabinooo.
Hi, THANK YOU so much for this, doing the above and re-uploading WordPress did trigger an upgrade and let me get into the Dashboard. I have been re-installing everything since, weirdly with plugins all back, the site didn’t error but was still just showing the menu and no page content.
I read online that the debug errors showing e.g. Fatal error: Uncaught Error: [] operator not supported for strings in Revslider plugin is sometimes caused by the PHP version not working, I dropped this down a few versions but it still wasn’t working. After leaving it overnight, it’s now showing everything except Revslider (slideshow) content so we’re almost there!
Thanks again for your help, I wouldn’t have been able to make any headway without at least getting back to the dashboard.