The decision element with the Caption “only 1 user role selected” should have a condition set in such a way that it yields a Boolean value. Think of it as a IF condition in the programming language world!
By looking the nice annotations in your microflow :), it appears that the condition you need is $NumberOfUserRoles = 1
Once you put this condition, then come out of the decision element and then save the microflow. Then you can right click on the line going to the right and select TRUE in it and the line going to the bottom should be automatically set to false
That should do it.
Let me know if it worked.
Also I recommend you go though the basic mendix training courses in the learn section to understand this more. if you have already seen them then do practice more :)
The expression should be $NumberOfUserRoles = 1
It looks like you might not have set any condition for your decision – simply open the decision by double-clicking and make sure you fill out an expression.