DID errors since recently on ISP phone line

Recently, all my calls stopped coming in. Calling my own DID, I get the “mobile number not reachable” recording. This seems like the call made it’s way through the network to my ISP, but my DID was not recognised somewhere in the chain. I tried setting the contact user to my phone number and my registering username. What can I do to troubleshoot? I know it’s wrong to set my phone number as the contact user, as that gives me the general “number not reachable”. I have made previous posts detailing my situation with my provider. Stuff has changed since then, as it didn’t register for a while and then registered again. I can call out fine. Noticed this when I left a voicemail with a relative, and they called on my mobile saying my home line doesn’t work.