Thanks for comment,
I checked with different browsers all had the same. Moreover when Grade submission is disabled student can login, the issue happens only when Grading is enabled either "homework" or "course".
WeBWorK Main Forum
Canvas LTI authentication broken after upgrade to 2.18
This forum has a limit to the number of forum postings you can make in a given time period - this is currently set at 10 posting(s) in 1 day