Google Messages - 3100 error

Google’s troubleshooting steps include turning RCS off, clearing data for “Carrier Services,” rebooting the device, and then turning RCS back on, but success seems hit or miss. Android Authority notes that one user details a six-step process that includes temporarily turning off 2-step verification and clearing Play Services data. While it apparently works, you should probably try Google’s steps before doing anything with 2FA – and you should turn that back on immediately if you do turn it off.

Google Messages RCS breaks with '3100' error for some, especially Galaxy switchers