Hello,
I was getting, "invalid network enrollment code". Yesterday, I tried the 3rd/4th option of sending an email invite and that seemed to work with getting the Service Manger to install.
However, now I'm getting, "For your security, your phone is not allowed to install unknown apps from this source." Both apps, Google Maps and a business software are in the Apps section to be allowed and updated. Barcode scanning and Meraki System Manager downloaded and worked.