Why Am I Being Investigated For Fraud On My Husbands Credit Account?

I am the DURABLE GENERAL POWER OF ATTORNEY FOR MY DECEASED HUSBAND and I had my own card,  I couldn't register the card online once I recieved them cause they had the security word wrong and when I called in I was shocked cause I was told the account was closed due to him being deceased and now it's turned over to the fraud department.  So am I in trouble for getting the card and using it? My durable power of attorney states that i can get loans, open accounts and sign hisname etc.!  So how can I be treated this way? Regards, Kim Walker