Import content failed error

I recentl bought a ebook from kobo and downloaded directly to my tablet and to ade where I authorized it with my account etc. After a week or so my library went blank and everything in it disappeared. Every time I try to upload again the file in ade it displays "import content failed" whether is the acsm file or the epub.

I tried everything. Authorization and reauthorization, re-downloaded the ade app to no avail.

On my pc and phone my library is fine and I can find the book there. It's just the tablet (and is driving me insane). I have a Huawei tablet for reference. 

Any recommendations? I don't see anything mentioned in this forum about this error?