Plusgram - Telegram
FAQ Entry
90

I cannot message non-contacts

If the other person has strict privacy restrictions, anti-spam protections, or you do not share any valid public entry point, you may not be able to message them directly.

In those cases, try connecting through a username, a mutual group, or an invitation flow.

Related questions

If this answer only covers part of your case, continue with related questions from the same topic. That usually makes account, installation, and security issues easier to connect and solve.