E_GOOGLE_DEVICE_LIMIT_REACHED

Hello! I hope if anyone could help with this issue! 

I have downloaded some ebook from Google Play Book and would like to put them in my e-reader.  However, during the process, I got the below error message. 

Unable to download Error getting License.

License Server Communication Problem:

E_GOOGLE_DEVICE_LIMIT_REACHED

I have searched the related articles here but it seems no solutions to this issue.  I have even tried to contact Google Support Center for help (someone said they helped before) but I got a reply that I should contact Adobe instead. 

Anyone could help please?  Many thanks!