EF6 "No migrations have been applied to the target database."

Well, the answer is that somehow during the refactor the namespace of ConfigurationDbContext changed from

demo10.Migrations.ConfigurationDbContext

to

demo10.Migrations.ConfigurationDbContext.ConfigurationDbContext

and the ContextKey column of the __MigrationHistory table should be the ConfigurationDbContext namespace (you can omit the DbContext, like to have

 demo10.Migrations.Configuration

in the table for

demo10.Migrations.ConfigurationDbContext

namespace).

Leaving an answer here as I had a similar problem that wasn't solved by this:

I had the password wrong in the app.config I was using against a different environment. Get-Migrations doesn't give you an error about failed credentials, it just tells you "No migrations have been applied to the target database", which is hugely misleading.

Hopefully someone else who comes across this will discover it's as simple as a typo in their connection string!

edit: the irony of typo-ing the word typo in an answer about my typo.