Cell phone doesn't accept incoming calls.

I have an ATT cell phone (Samsung S21 Ultra) and until recently an ATT land line.  I had the land line ported to a 2nd cell phone (U318AA from ATT).  From that second cell phone, I can call the original phone without issue.  However, from the original cell phone, I get a message that says, "Your call cannot be completed as dialed . . . Message 2 US01LV".  Sometimes it says Message 1.  I can check voice mail on both phones.  Text messages work both directions.  Internet connections work on both.

I haven't gotten a single incoming call on the new cell phone since it was set up.  I checked the settings to make sure I wasn't blocking incoming calls somehow.  Nothing seemed out of line there.

It's a very effective way to stop junk calls, but what's the point of having a phone if no one can call you?