New AT&T answering machine not picking up calls

We had an older answering machine and it stopped working so we assumed that we just needed a new one.  Well, the new one doesn't work either! We have checked with Spectrum who is our service provider and all of our lines show that they are working and there are no outages.  Our phones work but not the answering machine.  I'm at a loss as to why it won't pick up for customers to leave a message.  Any ideas?