Hey there MKHAIR,
Thanks for reaching out to Apple Support Communities. We understand you’re having issues using your cellular data as expected from your iPhone. We know how important it is to have this working as expected and we’ll be happy to help.
You’ve done some great troubleshooting so far. The fact that this affects multiple devices is interesting and could point to the issue having something to do with the Wi-Fi connection.
If resetting the network settings on your iPhone didn’t help, try restarting your Wi-Fi router and make sure it has the settings suggested from this link:
Recommended settings for Wi-Fi routers and access points
Also, check for a Carrier Settings update, and inspect the SIM card as stated in this article:
If you see No Service or Searching on your iPhone or iPad
We hope this helps.
Take care.