We are running on 2025 R2 version on both server & client version.
I know we can “Allow” it as a workaround. But wanted to fix permanently.
To fix it permanently you would have to turn on Encryption and you can do that using the Milestone Server Configurator in the server(s). Please consult the documentation on doing this. If you have further questions please please ask in the support community, you should get better help from the partners using the support community.