Hello hurry_,
Thank you for using Apple Support Communities. We want to help you with your Apple Watch. You've done a great job in troubleshooting this issue. From here, we'd like to recommend a few more steps we can try. First, make sure that you've properly set up cellular service on your Apple Watch: Set up cellular on Apple Watch - Apple Support
Set up cellular on Apple Watch
You can activate cellular when you first set up your Apple Watch, or when you set up a watch for a family member. During setup, look for the option to set up cellular, then follow the onscreen steps.
You can also set up cellular later from the Apple Watch app:
1. On your iPhone, open the Apple Watch app.
2. Tap the My Watch tab, then tap Cellular.
3. Tap Set Up Cellular.
4. Follow the instructions for your carrier. You might need to contact your carrier for help.
If these were the steps that you followed with no success, we recommend that you unpair your Apple Watch and re-pair it with your iPhone. Just in case, these resources can guide you through the unpairing process. Just a friendly reminder, all your data is automatically backed up when you unpair your Apple Watch. Once you set it up again, it will restore all your data back:
1.) Unpair and erase your Apple Watch - Apple Support
2.) Set up your Apple Watch - Apple Support
We hope these steps do help you. Thank you for using Apple Support Communities. Take care.