When I open Task View, the virtual desktop thumbnails appear blank.

Task View shows blank thumbnails for every desktop, including new ones, while restarting File Explorer restores them only temporarily. That makes an individual desktop configuration less likely; the evidence suggests shell rendering or the display driver, but does not identify which. First press Windows + Ctrl + Shift + B to reset the graphics driver, then reopen Task View. Install current Windows updates and any offered display-driver update. If the problem began after a driver update, open Device Manager > Display adapters > the adapter’s Properties > Driver and select Roll Back Driver when available. Disconnect any dock or external display and test again. Next, open an administrator Command Prompt and run DISM.exe /Online /Cleanup-image /Restorehealth, followed by sfc /scannow. If thumbnails still fail, report the Windows build, graphics-adapter model, whether it follows sleep or display changes, and both command results; those details are needed before recommending a repair installation.