Try to debug your code; there must be some missing value for some attribute.
please drop your microflow screenshot for a proper description of your question.
Check out the Access for the button with the user roles if that button calls MF or page
Take a look in the logs, you should see an error message there explaining what has happened.
In Studio Pro these can be found in the console, if you have deployed this up to the Mendix Cloud you will have to download them from there.
You should have a detailed log in the console with the cause of the error, most likely a permissions issue.