Hello @JennK04 ,
It sounds like you may be running into some connectivity issues when trying to access the site. Let’s start with some basic connectivity troubleshooting. Please keep in mind that when I say connectivity issues, I'm not necessarily referring to just your internet speed.
If none of those alleviate the issues, could you please provide a screenshot of your speed test, including the More Info section? Once we have that we can do some more advanced troubleshooting as needed.
You may also want to check that your contact list doesn't contain a bunch of empty columns, as that can significantly slow down or error out contact uploads from files. If you're not sure, try copying only the columns and rows with information in them into a fresh CSV file, and then upload that fresh file instead.