Just is case, take a look.
switch# show web
to see if HTTP or HTTPS is really enabled.
There should be a password, it could be local, radius or TACACS
Example if it is Local
switch# username webuser password password
switch# aaa authentication web default local
This is a video, that it may help you, also if https is needed.https://www.youtube.com/watch?v=YC8ZUoalvKk
I hope it helps.