Jitterbug phone on Lively

My husband is in assisted living. He has a Jitterbug phone that uses Lively as the service provider. Frequently when I try to call him as soon as my phone dials the number my phone immediately disconnects. No ring, no dial tone, just immediately disconnects. This doesn't happen all the time but it does happen more often than not. He can call me with no problems. I can call other people with no problems. I don't know what is causing this issue but it is very frustrating. Does anyone have any ideas as to what might be causing this problem? Thank you.