Windows 11 upgrade, itunes library not finding files

I recently upgraded to a new laptop running Win11. My itunes folder has always been stored on an external drive which the laptop can view in file explorer but iTunes isn't seeing the vast majority of the files. It does see some of them, which is weird, but the bulk of the library is invisible. The location of the itunes library is exactly the same as it was for the old laptop which had no problem syncing to this external drive, so is it the fault of Win11 or iTunes? I've searched the support pages and none of them seem relevant to Win11.