Why do some backlinks not show up on SEO Tool??

Im very new to SEO and Im using the Mangools SEO extension and it says I only have half as many Backlinks as I actually do, does anyone know why this would be?

All backlink sites are very similar and domain was properly inserted with https format

Maybe the tracker didn't find the Backlinks yet.
Or the backlinks are on page that block your tracker.

Because they are not Google. They don't have the resources to crawl the web as extensively as Google does. Most of these backlink checking tools only show a fraction of links.