At my company we have computers setup at each of our lines, each computer is signed into the same OneDrive account. There is a total of about 8 computers signed into the same account and each using a separate Excel file. It seems like each computer is taking a turn in signing out of OneDrive and there for the files are not automatically updating. After it is signed out it requires a restart of the computer and than signing back into OneDrive. It seems to be happening with a different computer each week.
Couple things. Hopefully all your users are licensed individually because sharing the same account is against license terms :).
On that note, how are you logged into each machine user wise? Honestly I wouldn't even mess with Sync if your using the same account like that, and would just have a link to the file or onedrive and access it via web portal since you're always going to be connected, remove that layer of complexity if it's not really needed (offline).