tldr. What works for me is Pausing and Resuming syncing from the OneDrive icon in the system tray. This is only a temporary fix as it does re-occur.
I have this same issue recurring with both OneDrive personal and my OneDrive for business.
I am on Win11 upgraded from Win10.
When all the normal OneDrive status symbols disappear and instead I get the the box symbol (maybe a storage/archive box?) overlay I can still click on them and they will download/open even if they weren't already on my machine, so doesn't seem to cause me an issue I just don't like not knowing what this is and why it happens. Having opened any given file the box overlay disappears. I am thinking it is in a not actively syncing state. So clicking on a file opens it, even downloads it if necessary, but is not constantly syncing any changes.
I have found a way to get back to the 'normal' situation, however it is not a permanent fix and so it does re-occur.
Click the OneDrive icon in the system tray (either personal or business)
Click the cog symbol to open the menu
Select Pause syncing for 2 hours
Wait for the 'Your files are not currently syncing...' message to appear
Click the cog symbol to open the menu again
Select Resume syncing
All files in both Personal and Business OneDrive now show their status symbols again, takes a few seconds as the sync process determines what is local vs offline and any changes.