A lot of mentions of "Settings > Privacy > Developer mode." Turns out, it's on the ACTUAL WATCH! On the watch, pressed the crown, then selected Settings (gear icon). Scrolled down to "Privacy & Security" then scrolled to the bottom > "Developer Mode." Toggled switch on. Prompted to restart. Answered yes to all trust questions. Quit Xcode and restarted, went to XCode > Window > Devices and Simulators, then selected Watch. It went through fetching Debug Symbols, then it was good to go. HTH.

Haha! Wish I could tip more than once. If it wasn't for your response I wouldn't have gone down the other path. Much appreciated!