The bottom of the catch cup falls out

It can be screwed on by twisting it clockwise.

Try to put your finger inside of the base and press it. At the same time, use other fingers to screw it inside.
Please refer to the link below:https://1drv.ms/v/s!Ao5P6d6BMg8Xgb0ZwzcHcFfafCSxiw?e=5sNicR