Shipper Migrate page is blank

I’m trying to use shipper for the first time. I’d like to move one of my site in another host to one of my site in the wpmu host. However, the source site Admin > Shipper > Migrate page is showing blank but I can see tools and settings.

I’m trying to import initiated from the wpmu side. The plugin is loaded on both and the source appears in the list. Preflight shows this error.

Service error: status: 522;

No remote data to process.