I can not add class to period of a timetable

hi there and congratulations for your nice job
I have problem adding class to period. I have created classes (as seen in pic1), I have created columns and rows in timetable (as seen in pic2) , but when I’m going to add classes to period it doesn’t appear any class under the dropdown menu (as seen in pic3). What am I doing wrong?
Thanks in advance

jonko, thanks for your kind words, and welcome to the Gibbon community.

The classes in the drop down are those that are tagged with year groups that intersect with the year groups that your timetable covers. Can you confirm that there is an overlap here?

Ross

Thanks for the quick answer and for the helpfoul answer. Ok. I fixed it thanks to you. thanks