Mailcious Web Site Alert

Hi, Within my organisation some users are receiving the above message when legitimately carrying out their work.

The above message opens in Internet Explorer, which is strange as the third-party application they use requires Mozilla Firefox. 

I clicked on the 'Symantec Security Response' and tried to answer the questions but none of the options reveal the above screenshot.

Running SEPM v.12.1.3001.165. Clients are running the same version. I understand this to be a False Positive but would like more information regarding action to take in terms of policy adjustments to prevent the message from re-appearing.

Many Thanks