Error 444 Connect to GCM

Hallo

I use the STRYD app for my workouts. When I try to load the workout on my Garmin Enduro (1st version), I get the error message ERR: 444 Connect to GCM. STryd support says it's a connection problem with the Garmin Connect app on my iPhone.

I tried the following:

Deleted the Garmin and Stryd apps on the iPhone and reinstalled them. The same with the STRYD app on the watch.

Restarted the watch and reconnected via Bluetooth.

When I run and record data, it is sent to the iPhone. Only the other direction does not work.

Does anyone have any ideas about this?

Thank you very much

Frank