Note: due to safety reasons, I can't name the name of the company or files...
I have a questions about site permissions. When we created the our company Intranet last year we were told that this would be a place where we could store documents available to all staff in "our company" but also to all staff in "our friend company" with in O365 account.
When we added security groups to the Intranet we added “Everyone except external users” to the security group which can read all content on the Intranet. Now, when I try to share link to the Intranet with colleagues in "our friend company" they say that they do not have access to our site.
Is there something that needs to be changed so that our Intranet will be available to all in our company with an O365 account?
First thing that needs to be clarified here is if those users are in your teanant or in another one. If the later is your case, that's the reason why any link you share with them is not working. What you have to do is to reivew your Intranet Sharing settings and verify that it can be shared with new and external users and then you should be able to share the Intranet with External users
@DiVojich If the users in "Your Friend Company" were created in your tenant then "All users except external users" would work. That it doesnt suggests they are external users and you need to enable external sharing on the Intranet Site collection. When you try and add the user do you get a message "This user is outside of your organisation" or something along the lines of "You are not allowed to shared this site with this user"
To enable external sharing go to the SharePoint Admin centre, search for the Intranet site collection and change the sharing settings. If the users already exists as external users in your tenant then you can select that option otherwise you have a few other options but I would recommend restricting the Intranet to the other company's email domain only.
This sounds like they are in another tenant if they are in another company. They can't access your site without first directly sharing it with users in the other company.
If they have accounts in your tenant as well what is most likely happening is there other tenants credentials are cached in the browser and they will need to use a chrome profile saved with your tenants account credentials or use inprivate browser when navigating to your site so they can enter the proper login.