Processus dans Microsoft 365 pour configurer des applications Office, entrer des clés de produit et activer des licences.
Hey there, Lucky Baron
I think I know what is happening. It looks as though they don't have a Microsoft account. Please can they create a Microsoft account by signing up here: https://signup.live.com/?lic=1
Once they have signed up and created a Microsoft account, please invite that new Microsoft account and they should be able to join.
Hope this helps,
Nathan