Phish Threat Addin still not working

Following this realease : https://community.sophos.com/phish-threat/b/blog/posts/sophos-phishthreat-now-supports-microsoft-exchange-2016-and-2019

I tested and it still doesn't work. Symptoms are identical : idle for 4-5 minutes to "is working on your Report to Sophos request" then it says to check network connection (while I obviously have a network connection). 

I know how to deploy an addin, no doubt about that one.

The client is O365 in version 2208 which I believe is the latest, the server is an on-prem exchange 2019. 

Not working both on OWA and client. 

I don't see anything blocked on our firewall. 

Regards,

A.