Brief summary of the bug. What is it ? Where is it ?

When using invalid username or password to login, the login button get disabled and no error message is shown to the user.

Steps to reproduce:

Try to log in to Optimize with an invalid username or password 

Actual result:

The button get disabled with no error message shown.

Expected result:

The button get re-enabled, and an error message appears describing the reason for the login failure.