That does now seem to be working . . . . I can only assume it may have been a caching issue . . . .
Thanks for your effort. I will now attempt to update other sites and hopefully it’ll work on all of them
… Updated this note - this is still failing on other X and Pro sites. I am deleting the Soliloquy directory and then re-installing the stock version (2.6.0) via the x/Pro menu. The plugin installs ok, then once activated any further action on the site results in the critical error.
I’ve tried clearing the cache on the server and at site level and also used different browsers.
I’m unable to repeat your success. I’d be happy to supply details for the further X/Pro sites with the issue.