How to Solve AdSense Login Problem

I have an active AdSense account. It was working fine. Suddenly yesterday when I was trying to sign into my account, I got the this message : " This user does not have an AdSense account. Please check that the email address matches your AdSense account address. New accounts may take up to 24 hours to appear. "

I tried again and again to login to my account but the same message is popped up every time. I got really very frustrated at that time. Then I searched Google to get any solution. Finally I got some info from a forum that it can happen due to low internet speed. Then I tried to login to AdSense in classic version and finally I successfully login to AdSense account.

Classic version of AdSense :- https://www.google.com/adsense/v3/m/classicui