Yep a screenshot of 'Your browser is being managed by your organisation' will help, as well as what DavidR said.
I don't think this screenshot is very useful, I think most firefox/avast users can show it to you.... like me here
However, as DavidR requested
I just wonder if you also have the Avast, Real Site or a VPN component/s ?
a screenshot of what happens when he tries to open paypal would be more interesting.
For example, because avast manages firefox, the Real Site agent imposes its own DNS on the DNS over HTTPS (DoH) function, it can happen that avast blocks ( safely or not) certain sites.
This is the case for me
https://forum.avast.com/index.php?topic=326957.0but as far I'm concerned,it doesn't block Paypal
Like said by avast team, it is difficult to reproduce the problem for each person, as the secure DNS are not the same for everyone and are allocated locally.