PowerPoint add-in is getting flagged as potential ransomware threat in my organization when shared on MS Teams

Question

I have a ppam add-in created for PowerPoint and after extensive development, I am ready to launch and deploy across the organization. For testing/pilot, I thought of sharing it via MS teams to a few of my colleagues. But somehow, my IT security team is receiving a potential ransomware threat intimation. IT says they have whitelisted the add-in in their firewall. But still after this, they are getting the same ransomware notifications.

On the contrary, I had digitally signed the add-in with some certificate available in my organization.(Didn't have to find or ask someone for the certificate, but when I tried to sign it, there was one available, so I used that to sign) Not sure how legit is that.

What else can I do here? Are there any other certificates that anyone would recommend?

Thanks in advance!