If you already have a TripMapper account:
Your travel agent must invite you to view your itinerary using your TripMapper account email address.
If you do not already have a TripMapper account:
You must sign up for the TripMapper account using the email address the travel agent sent the invitation to; otherwise, you will not be able to see the itinerary.
For example, if you create a new TripMapper account with an Apple private relay address, that email address will not match the email address the travel agent sent the invitation to, so you will not see the itinerary in your TripMapper account. If this is the case, provide your travel agent with your Apple private relay email address and ask them to resend the invite using your Apple private relay email address. The itinerary will then show in your TripMapper account (as the email address now matches 😉!)