eReader terminal authorization problem after password change

Hello!

I've recently bought my son a PocketBook ereader and, at the moment of authorizing it with our family Adobe ID, I had forgotten it. So I changed my password on the adobe website and troubles began : I can read on this ereader books bought AFTER the password change, but not BEFORE (even if I download them again) : I get the message "E_ADEPT_USER_UNKNOWN.

We've got 3 other ereaders and they accept book bought before or after the password change.

Any idea how to make the mew ereader accept old books? I've bought tons of children novels for my daughter, and I'd prefer not having to buy them again for my son...

Thanks for the help!

Ack