Hi Lauren,
Few quick questions that will help us better understand:
- It sounds as if you completed the installation of the Excel add-in, not that you are failing with the installer, is that correct?
- If failing to connect, are you using a SSO authentication or a native Rally authentication?
If native Rally then you shall use this URL: https://rally1.rallydev.com
If SSO, then you may have a different URL in which case you may want to check the connectivity between the machine that has the excel and that other URL for your SSO.
If you can include a screen shot with the failure, it'll help even more.
Thanks,
Sagi