First, thanks to all who provide the Dokuwiki platform.
I'm currently using the 'Elenor Of Tsort' version, but my server provider is recommending that I upgrade from PHP 5.6 to PHP 7.4. I tried, an it works on all my other websites, but it causes a PCRE error in Dokuwiki, meaning that pages can't be edited. The error message says that it may be a 'problem with a plugin' - but I disabled all my plugins and it made no difference.
So I tried to upgrade the Dokuwiki installation to the current version using the 'Upgrade Plugin'. All went well, and the plugin announced a successful upgrade. But the entire site now just displayed an blank page. No error messages, just a blank. (So I reverted to a backup.)
My ideal solution would be to keep the Tsort installation, but fix the PCRE problem.
Can anyone recommend a solution? My server company will eventually withdraw PHP 5.6, and the wiki will become unusable. Many thanks for any assistance.