Problem Redirecting from http: to https: - (JS)

Hi,
I have been trying to create a redirect to my companies’ site that would redirect a user to a secure page. The problem that is occurring is that if someone goes to our site (agentsonly.encorecruises.com) they are prompted for a username and password. Once they get passed that, they can then click on a link. Any link they click on leads to an encrypted page and for some reason they are prompted for a username and password again. So basically it prompts when the user is on the http side AND the https side. I just want the username and password to come up once, hence the redirect if someone types in agentsonly.encorecruises.com.

I am having no success and would welcome any kind of suggestions. I was not sure if I should post in here or on server side.

Cheers
Michael