New lutron dimmer cannot be added to group

I just added a new Lutron dimmer to my pro hub and added it into HE and I can control it through the device menu

my problem is that I want to add this new dimmer to others in some groups like "interior lights", but the new dimmer does not appear as a device that can be added.
Weird thing, if I create a new group, it apperas normally with all the other dimmers and switches.

How come I can't add it to an existing group and only to new groups ?

I hope I don't need to delete / recreate all my groups everytime I purchase a new dimmer ?

Thanks for any help