I used this link from your post: https://eontestnet.herokuapp.com/
The first screen was this:

the welcome screen, I clicked the x and went to the underlying screen:

Then I used the Login on top right hand side and got the regular login type screen:

Note the very subtle difference after I clicked login this screen showed:

It basicaly stayed in that greyed out state and did not log me in. It just sat there, when I clicked the browser refresh I was taken directly back to screenshot 2 above. I tried it three times, and just now a forth for this response. No error message nothing about wrong key or anything, (I used my posting key as the password.

I'll try again in the morning if I have time.