If you are getting a cert error, you can click on Advance and then Accept the risk and continue, you will be able to see the login page.
If still doesn't work, try to ssh into the AP using Putty or any other ssh tool, check the output of below commands.
rkscli: get https
HTTPs access is enabled
rkscli: get http
HTTP access is disabled.
if https still doesn't work, enable http on the AP with the command "set http enable" and test in the browser.