Issues Adding External Users to Communication Site

Hello,

I'm creating a SharePoint site for my orgs marketing department so they can share resources with a marketing agency we plan to use. Currently settings are set to "New and Existing Guests" and I was able to send an invite to my personal email for testing purposes but it does not allow me to access the site. It generated a guest account and had me log into a Microsoft page but when I entered the onetime code it just says that access is not allowed and more details does not offer anything useful. Any advice on settings I should check would be appreciated.