Hi,
We are fresh new user or Joomshaper products and our first experience is exactly with the same error/problem.
After many hours of searches and after waiting help from support without result, more than 2 days, we have found the solution : the Joomshaper products don't work with PHP 8.1+ .
After downgrade PHP to 8.0.27 the quickstart installation (Fixter) works. Just remains errors in the template whose cause are not necessarily due to PHP.
We therefore lost hours on this problem simply because of a lack of serious support : requirements should be displayed clearly in the details page of products or, at least, in frontpage!
Also, lack of reaction from the support during more than 2 days seems to be the rule...
32 jours after the request, one response: "Apology for the delay. Your questions will be answered soon in the forum post.", but at this time, 40 hours after the request, nothing...
It is clearly a deterrent to work with these products which seem, moreover, good products.
We know what hard work is and that nobody is a bot (as red in other post), but this type of problem seems to be very reccurent.
Sad...
Hoping the solution above help, and that the support "wakes up"
Best regards from France,
Henri