If the registry entry is created in a “First Run” it could be that that user for some reason isn’t doing the 1st run scenario for whatever reason, maybe because you had it as a service previously.
If you still have issues I’d suggest trying my alternative method I posted about July 30th.
I personally think it to be a superior method. Some people seem to dislike Junction commands mkLink, but I’m not actually sure why. In any case just follow the instructions from the post I quoted using your already moved location.
Oh, just a note, which may also be worth looking into with the other method too, you said the user has read & write permissions for the folder you’re trying to use, but look at who the owner is & make sure the advanced sharing settings are the same as a new folder you make on the C: drive root
