Plusgram - Telegram
FAQ Entry
89

Secret chat issues

If a secret chat cannot be created, first check both client versions, the network environment, and whether the chat is being started on a supported device.

Also remember that secret chats are device-level features and do not sync automatically across all devices the way cloud chats do.

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.