Error 500 - attempting to migrate from C-5 to C-7

I'm attempting to migrate from C-5 to C-7.
I did a cloud backup of my C-5, then shut it down and disconnected it.
I attached my new C-7, started it up and found the C-5 cloud backup, and clicked the Migrate button. I selected to migrate Zigbee and ZWave. It proceed and said the backup had been restored and was redirecting...then it landed on an Error 500 page.

I went to [my hub ip address]:8081/resetHub, logged in and did a soft reset. This brought up a green "Getting Started" page with "restore from backup" at the bottom. I clicked "Restore from backup", found my C-5 cloud back and attempted the migration again - but only selected Zwave - same result "Error 500"

What can I do next? Help

I think this issue is resolved. I did another soft reset, then started c-7 normally without attempting to migrate. Then I updated to the latest version of the hubitat software. Then did the migrate using Backup and Restore. That appeared to work. My system appears to be working now.