If your computer has the Windows 7 Sync Client (or is Windows 10) set to synch all files on OneDrive to your local computer and you don't have space for all the files located on OneDrive. The sync client will start to sync the files that have been added until it runs out of space on the C Drive. It will then display a message on your computer in the bottom right corner of the screen.
The OneDrive folder that was not able to be sync'd will show a red cross.
When you right click the OneDrive a new menu option will be available "View sync problems".
Note: If you have had a large number of files added to OneDrive it would be advisable to not bother with this option as it will be a very long list.
Below is an example of "View sync Problems"
This shows the files that were not able to be synced.
How to fix this problem
Right-click on your OneDrive folder located on your computer and select "Choose OneDrive folders to sync".
Deselect the folder that was having problems syncing due to size.
(Note It could be any folder that frees up enough space if you wanted)
OneDrive is now in sync minus the folder that was too large.
While it may not be possible to add the folder that was too large in it's entirety. You may be able to add some of the subfolders that are not too large.
At the bottom of the window, the client details how much space the folder you wish to sync will take up on your computer.