Activation error when trying to copy epub to DE

When I try to copy epub books (.acsm format) into my DE app I see an error message - Check activation.  It has been working fine before I had my laptop upgraded with the new SSD cloned from the old and the RAM upgraded from 4GB to 8GB.  I am guessing I might need to unintall & reinstall DE (V3.0.1.9134) but wanted to check if anyone has a solution before trying this.

Any help would be appreciated.

Cheers