I updated the app with a workaround. Regarding the bug filed, no one from Stack Exchange have gotten back yet. Poor support.

Looks like your Google account is not linked with Stack exchange.

There is a workaround for this. Once you have entered the credentials and staring at a blank page, go back to Settings and click Login again, this time you will be successfully logged in,

I don't know. Considering this is the weekend, I don't expect Stack Exchange guys to respond before Monday. Hopefully someone from the Stack Exchange team can respond to it soon.

This looks like a bug with Stack Exchange API. I have created a support request here: stackapps.com/questions/4438/…

@PM77-1 I also noticed issues with logging in. The issue seems to be with client OAuth flow of Stack Exchange API. After you put in your login credentials are you seeing an empty white page with title as "Login"? Yes, the app does support posting of comments. For future reference, you can email me with issues, the email is available in the app listing in Play Store.

@Cagentdog I have submitted the app to Amazon Appstore. Hopefully it is available for download shortly.