Why won’t my watch text people without iMessage?

https://support.apple.com/en-us/HT205547

1. To receive SMS, MMS, or push notifications from

third-party apps on your cellular Apple Watch, your paired iPhone must

be powered on and connected to Wi-Fi or cellular, but it doesn't need to

be nearby. You also need to be signed in to iMessage on your iPhone.

If you are trying to send/receive an iMessage (blue bubble) it can be off. If you are attempting to send/receive an SMS (green bubble) message the iPhone must be turned on but it does not have to be with you.

Is your iPhone turned on?