(Redirected) Windows 10 upgrade blocked by Dell Data Encryption

I implemented Dell's Data Protection/Encryption on the C:/ drive of my 30 month old Latitude 5400 series laptop in late-2014.  I disabled that same encryption mid-2015, because it detracted too much from overall laptop performance.  The Encryption console shows my C:/ drive now as "Not provisionsed.  

Now, I have attempted (multiple times) to upgrade my OS from Win 7 Pro to Win 10 via the current Microsoft 'free upgrade' offers.  However, the upgrade is blocked, every time, by the Dell Data encryption, as per the Win 10 upgrade failure report.  Doubly frustrating!  Is there any hope for resolving this?  Microsoft refers me to Dell.  Or, am I going to just sit back and stay with Win 7 until this laptop is eventually replaced?