Login link from client email is blank page

This plugin looks exactly what I need, so while I’m waiting for a reply to my pre-sales questions for the Pro version, I set up a user to experiment with the free version. I received the email with username and password and clicked on the login link from the email, but it just goes to a blank white page.

I have no problem paying for what I want but in my opinion it’s a disaster to have the free version so crippled that it’s impossible to evaluate the system, and the blank page on login has caused me to wonder whether the Pro version will even work at all.

Please advise, I need to make a decision quickly. Thank you.