I don’t have a real solution, but this has happened to me on my Moto G repeatedly over the last few years. People just seem to stop talking to me, then I reboot randomly and suddenly all these week-old texts come through. I just make a point of rebooting each night when I plug it in. Since that works, I’m guessing it’s a memory issue or some background process stops and never restarts, or maybe it loses some token and can’t communicate with the network. It’s weird they haven’t fixed it, but my phone is pretty old now so my expectations are low.