Joomla 3.10.11 - long in the tooth; Fabrik form error

[fabrikg09]

I maintain a small site that uses a Fabrik contact form I wrote ages ago.

After various updates of both the Joomla! install, Fabrik components and PHP, any submission of the contact form, instead of sending the form mail and displaying the expected "success" message, instead results in this:

The requested page can't be found.
0 get_parent_class(): Argument #1 ($object_or_class) must be an object or a valid class name, bool given

My first impulse is to push the PHP version backj to 7.4

Is this an error caused by an incompatiliblity with the latest PHP?

 

[lousyfool]

What PHP version are you using? Does it work with 7.4?
How did you update Fabrik? If you haven't yet, make a Github update.
Using any custom code of your own anywhere? Double-check it's correct and compatible with whatever PHP 8.x you're using.