Signal should periodically sync its contact list with the one in your phone. If it doesn’t, you cannot start a chat with someone who actually has Signal. Or instead of people’s names you will see their phone number in chats.
Perform the following steps to re-sync your Signal contacts.
1. Go to the Android Settings of your phone (these are the system settings, not the settings within the Android app!)
2. Choose Accounts.
3. Choose Signal.
4. Choose “Remove Account”. The alert of clearing data is incorrect, your messages will not be deleted.
5. Open Signal and tap on the compose icon. Your contact list will be empty. Pull the view down to refresh and update.
6. Your contact list has been re-synchronized
1. Go to File | Preferences.
2. Scroll down to the Contacts section and click on “Import now”.