By the look of your screenshot, your OnePlus 6 has not been updated for 2.5 years and appears to be running OxygenOS 9.0 or something close to it....
Update your phone to OxygenOS 10.3.5. See... https://forums.oneplus.com/threads/oxygenos-10-3-5-for-the-oneplus-6-and-6t.1266795/ (The above...
See stickied post.. https://forums.oneplus.com/threads/oxygenos-9-0-ota-for-the-oneplus-6.909533/ (If you cannot open the link in the OnePlus...
Go to... Settings > Apps & notifications > See all ??? apps > Google Play Store > Storage > Clear cache and Storage. Also, turn off any battery...
If it is not turning on or booting at all... it might be time to use the OnePlus un-brick tool, MSMDownloadTool......