Hi @sudosaurus
You're using the email indeed, but you're requesting other fields from Office 365 (Display Name, Business Phones, etc.). Power Automate will still try to find the user to fetch that information, and since it's a Gmail user, for example, it can't find it displays the name on Office 365.
You need first to check if the user is an Office 365 user. If it is, then you can collect all that information. If not, you can only collect the email since it's the only information you have.
To check you can do the following. First, get the information about that email from Office. If it can receive it, then you have information to save; if not, then it returns an error, and you only have the email. Here's what you need to do:
Global check:

Create a parallel branch:

Select "Configure Run After"

Then select it to run after errors.

Can you please check if and let me know if you have any questions?
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Cheers
Manuel