@Harry8-
It normally takes 24-48 hours after the guest has checked out for the host to receive an invitation to review your guest. Have you checked your dashboard and email to see if the notice is there?
If it has been more than 48 hours, I would reach out to Airbnb to ask them. The guest and host each get 14 days to complete a review.
The reviews are available to read once both parties have posted a review. For example if each of you post a review with 72 hours, as soon as the 2nd person submits the review, both will be able to view it right away.
If only one of the parties posted a review, that review (be it from the guest or host) will be posted on the profile after the 14 days have passed.
Has it been over 14 days since your guest checked out?