Thank you for posting this solution. It solved my update problem.Thanks for your help on initial steps. Appears fixed finally -- version 21H1 shows up under Settings/System/About on my computer.
I found the following link helpful to resolve the problem
Link tells you to open File Explorer, go to C:\$GetCurrent, and copy the Media folder to the desktop; then restart; then copy and paste the Media folder from desktop to C:\$GetCurrent; open the Media folder there, click Settings, then follow instructions for the upgrade. Took about 4 hours to finish.fol
I was not able to update my Windows 10 version 1909 to any later versions. MS's Update Assistant method was stuck at 99% for hours and went no further. However, it introduced the $GetCurrent folder in my C:\ drive. (My C:\ drive did not have this folder for reasons unknow.) So (1) I copied this $GetCurrent folder onto my desktop, renamed it to $GetCurrent0 to be sure that it would not be deleted or altered, (2) terminated the updating process with the Update Assistant, and (3) rebooted my computer. After the reboot, (4) I renamed the folder back to the original and copied it into the C:\ drive. Then (5) I clicked the Setup in one of the subfolders to start a new update process, following the directions given. The update was successful directly from version 1909 to 21H1, completed in about 3 hours or less.