Hello @Rod Hemphill ,
Guest users can see the directory under switch directory option only after they accept the invite. Could you please check if Invitation Accepted is "Yes" for the guest user by clicking on the user account in Azure AD? If it is "No", you can click on Resend Invitation button to get the Invitation URL and share that with the guest user to redeem the invite. This option is helpful if the invited user doesn't have a mailbox.
If Invitation Accepted is "Yes" and still the directory doesn't appear when you click on switch directory, try to sign-out from the portal, close the browser and sign-in again. If you still face the issue, try deleting the guest account and try to invite the user again just to make sure if the invitation is redeemed successfully.
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Please do not forget to "Accept the answer" wherever the information provided helps you. This will help others in the community as well.