Unable to add account

[kuchhai]

I am on macOS Sierra, Firefox 49.0.2. All three options to add a new account don't work for me. I've tried scanning a QR code with the MBP's camera, uploading a png of the QR code and entering the key manually and pressing Enter. Nothing happens. Please advise.

[inbasic]

Is this happening for all websites that offering 2FA or a single one?

[soumasandesu]

It looks like not related to which site causing the problem to me.
I use Firefox 51 right now and aforementioned situation exists on my Firefox too.