Hi, let me help you.
Please go to Settings > System > Storage > Advanced storage settings > Where new content is saved, and make sure "New videos will save to" points to a drive that exists and has free space. If it's set to a disconnected external drive or a folder that's gone missing, switch it back to your local C: drive. Then open File Explorer, look at Pictures, and confirm the "Camera Roll" folder exists inside it. If it's missing, create it by hand, or right-click Pictures, choose Properties > Location > Restore Default. Also check that the folder isn't set to read-only.