Issue with Blocking File Transfer in Skype Using FortiGate Firewall

[R_007]

Hello everyone,
I am currently finding a method to block file transfers in Skype. We typically use Skype for internal communications, but we want to restrict any form of file transfer within the application. All users are currently using Skype for Desktop, version 8.125.0.201.On research, I found that there is no direct method in Skype to achieve this. So we thought of achieving this using the firewall rules.

https://community.fortinet.com/t5/FortiGate/Technical-Tip-Block-file-transfer-in-Skype-while-allowin...
We found this post regarding blocking file transfer using FortiGate firewall. The option to set up application filters and overrides was available and everything was set up as instructed in the given link, but when tested FortiGate did not block file transfer in skype. We are currently using FortiGate Firewall version 7.0.13. We are unsure how to proceed with blocking file transfer in skype using firewall, other than this.

https://nhanthang.com/blocking-skype-file-transfer/
We also tried to download and import Skype ADMX files into Group Policy to manage settings, but this did not seem to work. The ADMX file was for a very old version of Skype. And we were unable to find the ADMX files of the latest version. Followed the following link above, but still no luck.

If there are any other methods or best practices to effectively block file transfers in Skype, I would greatly appreciate any insights or suggestions.
Thank you in advance

[AlexC-FTNT]

Make sure your 'deep-inspection' SSL-SSH profile does not exempt Microsoft websites (the default profile does exempt some)