Why isn't SMS an option for two-factor authentication?

I have the same problem. It was originally working for years and it stopped working now. I tried to go into Zoom, after entering my password, the 6-digit code did not come by SMS on my phone. Had to use 1 of my recovery codes to get in to turn off 2FA. When I turn 2FA on again, I am not able to select SMS as an option. Why?

I seem to be having an issue that SMS does not appear as an option for 2FA. How do I get SMS to appear as a 2FA setup option? My profile has my phone number entered.