I don't get the login box. The full script passes username and password, or would if it could download that first page.

Yeah, it's hard to perform any meaningful test from here without a valid username and password.
Even if I change the url (in the script you provided) to:

https://sourceselfservice2.ceridian.com
[download]

I still can't even browse to that. All I get is a redirect to:

https://sourceselfservice2.ceridian.com/en-us/Invalid.asp
[download]

and an error message that says:

This request is not valid.
Please close this window and log back in.
If you feel that you have reached this page in error, please contact y
+our administrator.
[download]

Sort of suggests to me that you have to be logged in *before* you can even get to that page ... seems odd, but I don't know much about the way these things work. (Magic, I expect ;-)

Maybe you need to shift your investigation to trying to understand how on earth it is that the old connection worked.

Cheers,
Rob

On the old system, I could download the page, then populate the form and post. On the new system, I can't download the page. The fact that the page loads on your system, and shows the login form, implies your setup is working better than mine. Are you able to share what packages are loaded to support https with Mechanize?