Hello one-of-8.
Thank you for using Apple Support Communities. We can understand how not receiving text notifications would be an issue. Allow us to investigate this issue and assist in any way we can. We'd like to gather some additional details from you. When this issue occurs, does it occur with all contacts that send you a text? Is this issue only occurring with SMS text messages (green bubbles) or iMessages as well (blue bubbles)?
Does this issue occur with both Wi-Fi or cellular service or both? You did mention that restarting your iPhone didn't help. Let's attempt the following steps. Navigate to Settings > Notifications > Messages and turn off Allow Notifications. Once it's off, navigate to Settings > General > Reset > Reset Network Settings. This also resets Wi-Fi networks and passwords, cellular settings, and VPN and APN settings that you’ve used before. If you're using iCloud Keychain, these settings are also removed from other signed-in devices.
Your iPhone will restart during this specific reset. After it resets, you will need to reconnect to your Wi-Fi network and turn on notifications for Messages again. Test to see if that helps both on Wi-Fi and on your cellular network.
Keep us updated on your results. Best of luck.