Not every video exposes the same set of thumbnail files. A missing high-resolution option does not necessarily mean that you entered the wrong link or that the downloader failed.
Read what the tool found
ToolNivo probes several known image variants and lists the ones that load with usable dimensions. It excludes tiny placeholder results. The resolution menu reflects those checks rather than promising a fixed largest size for every upload.
Use the best genuine source
Compare the available images at the size needed for your task. A smaller version may be sufficient for a reference sheet. If you own the video and need a larger editable image, look for the original thumbnail export or project.
Avoid false upgrades
Renaming a file or enlarging its pixel dimensions does not restore missing detail. Keep an upscaled derivative labelled as such if you create one. When no result appears, verify the video URL and try the direct image-opening route before assuming a larger original exists somewhere behind the unavailable option.