I've rebuilt the carburetor, but I think there is a part missing. In the photo, at the top of the carb, is the plastic arm that rotates the choke. Shouldn't there be a return spring on it so it will open again
Where the chok is activated by over run on the throttle control you need a return spring
On mowers with both a throttle & a choke control you do not need one.
Not familiar enough with your mower to be defintate but that is what is the general case.