Hi, @Dom ,
First we recommend you the check the settings of OneDrive. Right click the icon of OneDrive and select "Settings", then go to account tap and click "Choose folders". Check if the folder need to be synchronized is selected.
If the issue is still there, please check the size of the folder. The size of the folder should not be larger than 15GB.
We also recommend you to have a check if the version of OneDrive. Right click the icon of OneDrive then choose Settings->About. If the version is not the latest version, please update the OneDrive version.
Also you need to have a check if there is any updates for Windows. Press Win+I then choose Update&Security to check if there is any update for windows.
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