You must have one of the Stryd data fields to get power on your watch, to properly activate Stryd and for data to show up in the Stryd platform. You can only have one data field active at any one time.
On your Garmin watch*, go to Settings > Activites & Apps > Run > Run Settings > Data Screens.
Hit the top right button to edit the data screens. Scroll to the field which shows Stryd power. Select that field by hitting the top right button. Select a metric such a distance (not any of the Connect IQ options).
Make sure to leave one of the Stryd data fields on your watch for Stryd to work properly.
* These instructions are based on a Garmin FR645. Other watches may have slightly different naming and buttons but will have similar functions.