There are a couple of reasons why you might receive an Invalid Profile error while enrolling in Apple devices. This article lists a few of the causes and solutions to help with troubleshooting.
Problem: Apple Enrollment Profile needs to be refreshed.
Description: Apple purges old enrollment profiles from their servers every now and then.
Solution: In Securly MDM > Organization > Settings > Apple DEP tab > click on the name of the DEP account > DEP Tab > click Update DEP Settings at the bottom of the tab. Please wait for the sync time to change.
If any of the devices that you tried to enroll and received the download profile failed, you will need to hook these devices to iTunes or Configurator and perform a "Restore as New". https://support.apple.com/en-us/HT201252