access – sharepoint online notifications to external user permission issue

My goal is to enable up e-mail notifications for sharepoint online to external users. This is done with succes with admin account. But if a regular user inside the organization want to set up notification for external account she gets an error:”Sorry you do not have permission”.
And if i go to admin account to check the test folder permissions it says “full access” under permission level.
Yes she can ask for permission, and it is request for is groupwebsite (i hope it is understandable translation) and then i have to select from the drop down list but what more can i give after “full access”?