Send an error log to samsung. When they see its an issue that more people are having they may fix it. It stopped working for me on 2nd Jan. Note 20 ultra. I'm with EE who sent me a new sim, didn't fix. Factory reset didn't fix. EE in the end changed my phone number, said it was last option. It worked for 8 days then stopped. few weeks back I finally connected to Google. It worked for a few days until I set samsung to default. chat was not working. went back to Google which won't verify my number again. My last error log they told me to contact my network again. Its not the network. I'm sure of it.