Trouble with guest access to SharePoint site

[Jennifer_Head]

Greetings,

I am having a terrible time getting my colleagues access to the SharePoint site that I created for our collaboration. I've been on the phone with Microsoft Support twice and they are still getting error messages when trying to access the site. We have the permission for the link set to "anyone with access" and I added one of them via protal.microsoft.com admin center. The site shows that she is added and she can still not access the site. It would be FAR superior to using Google Drive, Docs, and Sheets for this collaboration. We are working on a textbook together. It's a complex project. 

Has anyone encountered this issue?

Thank you in advance!

[#2]

Hi @Jennifer_Head - can you clarify a few things?

1. Are they truly guests (external) to your tenant or are they users in your tenant? 
2. How did you add the one user in the admin center? Were you creating a user account for them or adding them to a security group that has access to the site, or...?
3. How did you grant access prior to the 'anyone with access' links were shared?

If you create a sharing link that's for anyone with access, you're essentially sending a link to someone who has already been added as a member, visitor or owner of that site. Anyone who hasn't been added to the Site Permissions already will not be able to use that link.