[SOLVED] Auto Actions 403 error

Relatively new to Joomla!, and very new to CB (1 month). Cannot find similar problem in forums.
I have a simple site with 115 users, simply to be used to record and display member contact details, and use Group Jive to allow groups to be formed and events to be registered.
When setting up my first Auto Action to add new users to a Group Jive group, selecting GroupJive as type results in 403 error. Subsequently found that simply attempting to save a new Auto Action resulted in the error.
I have updated CB, and GroupJive plug-ins today, and error still occurs. I have uninstalled Auto Actions and reinstalled - still get the error.
I can edit or add items in Group Jive, so that plug-in seems to be working. I have run the various CB tools to check CB database tables, and everything returns ok.
I have checked file permissions via my hosts cPanel, and everything is 755 as originally installed.
I cannot seem to understand what resource cannot be accessed, and not sure where to look.
When first set up main folder had password protection - this has been removed but error still occurs.
Can you suggest what to look at next please.
Regards
Alan

Joomla 3.9.26
PHP 7.4
MySQL MariaDB 10.3.28
CB 2.6
GroupJive 3.5
AutoAction 8.1

Are you seeing something like "403 Forbidden Access to this resource on the server is denied!"? If so that's a server error. Specifically it's an error from mod_security. Contact your host as they'll need to make a mod_security exception since it's blocking CB Auto Actions.

Thanks for your advice - I’ll get on to my hosting service

Described problem as you suggested - host whitelisted some rules - seems to work now.
Apologies for no-technical description - thank you very much