I’m getting exactly the same thing. Was working fine but then stopped a few days ago. I’m unable to access anything in OS Ticket so can’t even say what version it was running because the above errors prevent me from accessing it in any way.
So I upgraded OSTicket to the latest version, which worked fine, then uploaded the latest version of OSA and bang! Same issues.
So I’ve had to back it out.
Something in OSA is causing these problems – I’m on CentOS7, cPanel latest version and PHP 8.0.