Hello Sidhant Dorge,
In the screenshot that you have shared, I can see that you have added page validations for New Password and Confirm Password fields. Usually in Mendix, whenever your page validations fails, the onchange microflows are not triggered. Can you try one thing? Can you please either remove the page validations or try to fill all other values in the page and then try to change the UserRole field. That should trigger your On Change microflow.
Thanks and Regards,
Praharaj Mahaprasad Tripathy