My phone rarely receives texts on its own and I must send a text usually to myself to get it to refresh and send me messages. I've been texting a huge amount in the past month but idk if that is relevant. It has also gotten much worse over the past week.
And if these options don't work, then try testing a new sim in the phone as it might get a better connection to the network thus allowing the voice network to work correctly. Hopefully you don't need a new sim but it's worth a shot!