I tried cookies set to 'accept all'. I lowered security to minimal. Made no difference. I'm using mozilla firefox. I found other posts with the same problem. Looks like it is well known with no fix.
Pop up only appears for a second, and it usually says "you are logged in satisfactorily". Or it says " you are now logged in. Happy clipping.". Yet red dot still there! If I try and open web clipper again pop up opens only momentarily.
I assume that this sudden closing of the pop up after half a second is part of the 'bug'.
This makes evernote unfit for use for me.