The provider did not return a ProviderManifestToken string error

The problem was with the MySQL connector/Net.

I previously used MySQL connector/Net 6.3.5 and after I uninstalled it and installed MySQL connector/Net 6.5.4 the issue was fixed. You can find latest connectors at http://www.mysql.com/products/connector/

I know this may be very basic for a couple of you guys, but this exception is also thrown in cases where EF is unable to locate a Connection String to use. If you-re working in a multi-layered application, make sure the connection String is added to your client application, instead of the class library that contains you data access code. Just my 2 cents.

You can also get this error if you upgrade Nuget references in an EntityFramework project that uses MySql.Data.Entity (latest version is 6.10.X) and MySql.Data (latest version is 8.0.X). Those version numbers should match. You should use the MySql.Data.EntityFramework package with MySql.Data version 8.0 and after, and the MySql.Data.Entity package with versions 6.10 and before.

There are a lot more details in this blog post: https://davidsekar.com/asp-net/mysql-error-the-provider-did-not-return-a-providermanifesttoken

I got this error when my sql server was actually down. So, please be sure that your sql server is up and running.