The root cause could be a single misconfiguration or a combination of factors. Below are a series of steps — each one might resolve the issue. After completing each step, restart your computer and try opening the model in Revit again. If the problem persists, move on to the next step.
Try opening the model while logged into Windows under a different user account.
Update Windows to the latest available version.
If the issue started after installing new software, try uninstalling that software if possible.
Update Revit to the latest build or patch.
As a last resort, reinstall Revit.
(Alternatively, using a different Windows user account might be easier.)