I’m having an issue with my Apple watch series 5.

Erase the watch

1. On your Apple Watch, tap Settings > General > Reset > Erase All Content and Settings. 
2. 
   
3. 
4. Type your password if prompted.
5. For GPS + Cellular models, choose to keep or remove your cellular plan.

• • If you want to pair your Apple Watch and iPhone again, keep your plan. 
• If you don't want to pair your Apple Watch and iPhone again, remove
• your plan. If you aren't going to pair with a different watch or iPhone,
• you might need to contact your carrier to cancel your
  • cellular subscription. 

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2. Tap Erase All to confirm. This resets your Apple Watch to the factory settings.

If you already gave away your Apple Watch, you can erase and turn off Activation Lock from iCloud.com. Here's how:

1. On a computer, go to Find My iPhone on iCloud.com and sign in with your Apple ID. 
2. Select All Devices, then click your Apple Watch.
3. Click Erase Apple Watch. Select Next until the device is erased.
4. Click the X button  next to your Apple Watch. 

Learn more about Activation Lock. 

See How to erase your Apple Watch if you don't have your iPhone

If you have taken the watch off your iCloud

and you erased your watch as per the instructions above

Then it should have nothing on the watch.

Try erasing it again.