Fatal Error on updating to new version – URGENT

I have just updated to version 3.5.9 and received a Fatal Error message on www.kismetwellbeing.co.uk "Fatal error: Uncaught Error: Attempt to modify property "response" on bool" It is a longer message which I am happy to email through direct if it helps. I got the same message when updating a site that uses Rock Star Pro. On each site I am using; WordPress version 5.8.2 Current theme: Catch Fullscreen Pro (version 3.5.8) Current plugin: (version ) PHP version 8.0.7 It appears that the changes made need URGENT attention. Thanks, Chris