An incomplete watch URL can look plausible while containing no usable video identifier. A sharing parameter alone does not tell the downloader which video to inspect.
Check the source address
Return to the individual video and copy its link again. A standard watch address identifies the video through its v parameter. If a message contains only a watch path and unrelated parameters, the missing identifier cannot be reconstructed reliably from that text.
Avoid manual guessing
Do not copy an identifier from a nearby recommendation or another browser tab. This can produce a valid thumbnail for the wrong video, making the problem less obvious. Use the original video's share action when possible.
Verify the next result
Paste the fresh link into ToolNivo and compare the preview with the intended video. If the link is accepted but no image loads, treat that as a separate image-availability or connection issue. Correct URL parsing confirms the identifier's format; it does not guarantee that the associated image is accessible.