Max. Device limit reached - Deactivate non accessible devices

Hi there, I got my ebook reader into repair and they did a full reset. So I tried to activate my Adobe ID on the reader but got the „ max device error“. As a found no clear path to get a list of all my registered devices or a way to deactivate all my devices, I reached out to you on twitter (@adobecare). They sent me to this forum, to post my problem here. 

So is there a way to get a list of all my associated devices or to deactivate all devices in self service? If not, how can I reach out to the Adobe service? I did not find any type of emailadress or support form on the homepage.