Have a problem online diagnostics on my Precision 7720 Mobile workstation. Seems to have started after applying BIOS 1.14.1 which only partly succeeded.

BIOS itself was updated from 1.13 to 1.14.1 but part way through, the ME firmware update component failed and now have following message after POST appearing for several seconds at each cold boot:

Error sending End of Post message to ME: HECI disabled, proceeding with boot

Since that time, I cannot use Dell's online diagnostics with the following silly message appearing despite using 64bit Win10: 

Diagnostics cannot be run on the device you're using. The diagnostic application works only on PCs running Windows 10, Windows 8.1, or Windows 7

Have tried reverting to old BIOS and updating through Optimizer but same issues

Any thoughts