Hi there!
Sorry for your issue.
I have checked your backend and you are using Melvin template there, we do not have any template named Calvin:)
However, I have opened a few pages randomly with edit mode and those are working at my end, I could save changes.
Would you please let me know which page causes issue for you? A screenacast will be better to understand the issue.
Moreover, you are using PHP 8.1 version there. The Melvin template is not compatible with PHP 8.1 fully, it will get the compatibility soon. You may try with PHP 7.4 for now. Here is our plan: https://www.joomshaper.com/blog/latest-php-compatibility-for-templates-and-extensions
And we are on the way of bringing the plan live. Here you will see some blogs about it:
https://www.joomshaper.com/blog/releases-updates
Best Regards