Agreed. When I joined SA & saw their suggested link to my brokerage account I fired-off an affirmative refusal and ran like hell. What a risky mistake that would have been. 

Finally able to log-in SA via Chrome. Not convenient but it functions.

Also, don't waste your time calling SA Support at 1-347-509-6837 (New Rochelle, NY 10801) not India, no one will answer and the voice mail mailbox is full.

I have the same issue & greyed-out screen in Win 10 on both Firefox & Chrome but attempts to log-on with Google defaults to fruitless further "Authentication Required' plus sending duplicate SE emails to my Android phone.

I suddenly can not access Stock Portfolio Tracker. It requires further autentification even if I am logged in.

I left the page open, opened a different prior email from Seeking Alpha & clicked on "enter" pop-up sign-in form already filled-in & it allowed me to post my comment. Since then "SA" has stopped asking me to log-in each time which is just as well because I am not sure of my current pass-word that is shown as dots.

So I guess for now, problem solved until the next time a sign-in pop-up appears.