If you have deployed it to the cloud (dedicated note) you can press the Change MxAdmin Password button
Or if you are deploying it to localhost you can change your PW in Project→ Security → Administrator
If it is the first time to deploy to a Sandbox environment it may be needed to initially create an admin account hard coded in the AfterStartUp Microflow.
The application was deployed on premise. During the initial deploy, I set the password but unfortunately, I forgot what it was. I am wondering if I change the password in Mendix pro and deploy it, does it change the password as well?
I’m not sure how your configured on premise enrironment is built but I would give it a try to change it via StudioPro and if not just Retrieve the Admin User in your afterStartup and give it a new password.
Or did you think about implementing such a module (in case you users forget theirs as well):