No, I couldn't get that far. I performed some additional troubleshooting and it appears that the failure was happening at the step where we create the project:
Azure Migrate > Servers, Databases and Web Apps > Create Project
We have a default policy in place that requires Tags on new Resource Groups, and there was no way to add Tags when creating a new Resource Group via this workflow. Manually creating the new Resource Group (with Tags) worked, and I was able to successfully create the migration project and begin discovery.