Connecting Runna App to Garmin

I have trouble connecting the Runna app with my Garmin. 

In the Garmin Connect app, Runna does not show up under apps that are or could be connected (it works for Strava and Komoot though). 

When in the Runna app, klicking on Sync to Garmin, I get directed to a Garmin-SSO, correctly enter my password and always get the message "An error has occured. We could not give this application the permissions you requested."

It's very annoying, I want the freedom to flexibly use Garmin with other third party applications. Is there a fix for that?