No "I know the remaining blue words" button in certain lessons

See the screenshot.

The lesson is Login - LingQ - I’ve imported and shared it a while ago.

The same is true (no button) for all the lessons in the course ( Login - LingQ )

The same with this one: Login - LingQ

So it doesn’t have to do with who shared it.

Thanks Eugrus, looks like the button doesn’t appear in some lessons on Classic reader. We will get it fixed.
In the meantime, if you switch to new reader, all blue words became known automatically once when you complete a lesson.