Have you tried:
– deactivating all plugins to see if this resolves the problem. If this works, re-activate the plugins one by one until you find the problematic plugin(s).
– switching to the default theme to rule out any theme-specific problems.
– resetting the plugins folder by FTP or PhpMyAdmin. Sometimes, an apparently inactive plugin can still cause problems.
– re-uploading all files & folders – except the wp-content folder – from a fresh download of WordPress. Make sure that you delete the old copies of files & folder before uploading the new ones.
I inactivated all the plugins and the post template is now working. I have not started the task of activating them all yet to learn which one is the culprit because I have some other issues to repair first. Thanks. This is resolved.
