microsoft 365 e5 instant sandbox +Azure Active Directory + Invite External User + Bookings

Hi Team,
I have configured a M365 Developer Instant Sandbox, I managed to configure Booking page, I'm able to invite internal staff members to my Booking page but if I try to invite external users it seems to not work.
I'm able to invite an external user in Azure Active Directory, I added the license Microsoft 365 E5 Developer (without Windows and Audio Conferencing) but I'm not able to add the user as a staff member in my Booking page.
Am I missing a configuration? Is it possible to add external users, assign licenses and apps to the external user through M365 Developer Instant Sandbox?
Thanks!