I have a similar issue. I might have found something to help. I copied the name of the file giving the error and searched my hard drive. The file popped up in a different location. So the file still existed on my hard drive and I can open it from this location. It appears, for me, that the files with the x in the one drive folder are a sort of ghost file from the sync process that is no working. My problem was a titch more complicated as I am at work, on work computer. Several layers up the food chain, the powers that be chose to change the name of our company wide path. Meaning, sync was broken, took a while to discover sync not happening, there is no longer a one drive with the original name to reset a connection to. I thought files were gone when I was just seeing the ghost file from the sync process. I believe in the end I have recovered all of the files.
Hope this helps someone!