Hi mm4653,
When this happens is your Apple Watch connected to your iPhone using Bluetooth or is your iPhone out of range? Are you using a GPS + Cellular model? We ask since behavior is a bit different depending on model and whether or not your iPhone is paired via Bluetooth. The article above, About Bluetooth, Wi-Fi, and cellular on your Apple Watch - Apple Support, mentions the following.
"Your Apple Watch uses Wi-Fi and Bluetooth to communicate with your paired iPhone. If you have cellular, your watch can also stay connected through a cellular network. Your watch switches between these intelligently to choose the most power-efficient connection. Here's how:
- Your Apple Watch uses Bluetooth when your iPhone is near, which conserves power.
- If Bluetooth isn’t available, your Apple Watch will try to use Wi-Fi. For example, if compatible Wi-Fi is available and your iPhone isn't in Bluetooth range, your Apple Watch uses Wi-Fi.
- If Bluetooth and Wi-Fi aren't available, and you set up a cellular plan, cellular models of Apple Watch can connect to cellular networks."
If the same continues and it seems that your Apple Watch should be automatically joining the network using the information above, try unpairing then pairing your Apple Watch again. This might help refresh your settings and resolve the issue. You'll find the following guidance in Unpair and erase your Apple Watch - Apple Support.
"How to unpair your Apple Watch from your iPhone
- Keep your Apple Watch and iPhone close together as you unpair them.
- Open the Apple Watch app on your iPhone.
- Go to the My Watch tab and tap All Watches.
- Tap the info button next to the watch that you want to unpair.
- Tap Unpair Apple Watch.
- 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.
7. Tap again to confirm. You might need to enter your Apple ID password to disable Activation Lock. Before erasing all content and settings on your Apple Watch, your iPhone creates a new backup of your Apple Watch. You can use the backup to restore a new Apple Watch. After your Apple Watch unpairs, you'll see the Start Pairing message.
8. Set up your Apple Watch again."
Take care.