Learm Responsive Design: Lesson 2 - EM

I cannot pass this lesion as per scanning code bug?
This lesion is explaining the use of relative sizing of the elements and therefore is asking to change the size of particular headings in a banner to 1.5em. After I’ve done it, clicked Run button, it can’t recognize the changes that I made and I can’t go to the next lesion.

Also I think would be important if I mention that at the beginning of this lesion, I’ve noticed that the code runs itself for the first time (like it has been clicked the Run button) and mistakes were highlighted.

any idea?

Just noticed, the code is recognizes only AFTER I reload the whole page via the browser reload button. This might help other users also.
It’s happening with the next lesions from the same course as well.