Cannot import acsm (epub) books to an authorised phone / tablet

Hello,

I haven't been able to import epub books (acsm files) to authorised devices for quite a while.

I have tried different apps (Aldiko Reader and Bluefire reader), does not work in both.

I have tried in 2 different Android phones and an Android tablet, does not work.

I have formated my phone and tablet and re-installed everything again, does not work.

It shows the progress bar for the import, but it does not move. After a while it gives me an error message: The file could not be imported.

It worked before on the phone / table I am using now. Why did it stop working? Could you help me with this?

Thanks.