Hi @CorentinRICHARD, thank you for reaching out.
To access your Deezer account, you will need not only the email but also the password. Are you logged in with your Google account associated with your Deezer account? Or are you doing a smart login?
Regarding connecting Deezer to your Garmin watch, please follow these steps:
-Open the Garmin Connect app on your smartphone and tap the menu icon located in the top-left corner.
Note: On iOS devices, you will need to select "More" first.
-Select "Connect IQ Store".
-Search for the Deezer app.
-Select the app and download it.
For more detailed information about this procedure, please refer to our article " Deezer On Garmin" to view all the necessary steps.