Board Game Arena

Asking for my wife, who never played the boardgames but loved the BGA implementation:

When she picks minor/major improvement space (in a solo game), some occupations can not be chosen for some reason (even though she has enough food to pay for it). Is there some rules we are not aware of?

The yellow Occupation cards can only be played via "Lessons" action spaces.

The orange cards are Minor Improvements and can be played via improvement actions.