A Microsoft file hosting and synchronization service.
I used Claude AI to resolve this issue by feeding in all the information. The solution it came up with was to format the SD (D: drive) as 'NTFS' instead of the default 'exFAT'. So I backed up the SD, reformatted and reconnected to OneDrive. This worked. I am very disappointed that Claude AI was able to resolve the issue in such a short time when Microsoft's technical support team was unable to resolve the issue in over three months and closed several tickets without resolution! I guess it is true that AI will be replacing technical support jobs sooner rather than later.