Minecraft Account Syncing

Same issue here. If I log into Minecraft on my Nintendo switch under my Nintendo account, I can see the DLC. But it will not sync over to my Microsoft account to be able to play on different devices.

Has anyone had luck syncing purchases made with a Nintendo account to a Microsoft account in Minecraft marketplace?

Did you get your minecraft working? Mines doing the same thing, I loaded minecraft with another account and it worked, but my account stays on the sync screen.

I think the issue on this is due to the save data. Since Xbox Live backs up the console data and makes it available on cloud for download it would be how he would get it on his PC. It sounds like his PC isn't getting the most recent version of the save
data from the cloud. Depending on your internet speed it could take a little while to sync a Minecraft world to the cloud. Try leaving the Xbox turned on for a little while and give it some time to fully sync. On the Xbox you can also use the menu button to
view the manage data and see user data as well as save data and make from there you will be able to see the most recent locally saved data and the most recent cloud data, if both of those are showing the same then at least you know its the proper save data
in the cloud. If all of that worked, he might need to see if he can redownload the synced data on the PC version, but if I had to guess the issue is likely on the data just waiting to be uploaded to the cloud from the Xbox.

try to log out and in again on his profile on his console, that should do it

Tried that, didn't work.

try to log out and in again on his profile on his console, that should do it