Unable to mark optional ungraded lab as completed - A brief Python refresher

I finished reading the ungraded lab “A brief Python refresher” and i clicked in mark as completed button but for some reason with that lab specifically, it’s not working, could you please check this out? thanks

that green tick mark for ungraded lab will not happen, but don’t worry if you run down the codes completely, it will be marked as completed.

this is a known issue and was reported by tester. please continue your learning.