Hello!

When I write http://dnndev.me/ in the browser I get Connection To The Database Failed

This dnndev.me worked for a week ago and I haven't done anything that should cause this problem but obviously I must have done something.

The connection string looks like this 
<add name="SiteSqlServer" connectionString="Data Source=.\SQLExpress;AttachDbFilename=|DataDirectory|Database.mdf;Integrated Security=True;User Instance=True" providerName="System.Data.SqlClient" />
and it's the default connection string.
I If I enter SSMS and use server name =localhost\sqlexpress and try to attach to the C:\Websites\dnndev.me\App_Data\Database.mdf  I get 

The database 'C:\WEBSITES\DNNDEV.ME\APP_DATA\DATABASE.MDF' cannot be opened because it is version 869. This server supports version 663 and earlier. A downgrade path is not supported.Could not open new database 'C:\WEBSITES\DNNDEV.ME\APP_DATA\DATABASE.MDF'. CREATE DATABASE is aborted. (Microsoft SQL Server, Error: 948)

If I now use SSMS again and instead select localhost for Server name and attach to C:\Websites\dnndev.me\App_Data\Database.mdf it works fine.
If I right click on localhost (SQL Server 14.0.1000) and select property I can see that the Name is AF-7BSCGH2\SQLEXPRESS01.
So because its SQLEXPRESS01 i tried to change the connection string see below.

So i tried to change the connection string to this 
<add name="SiteSqlServer" connectionString="Data Source=.\SQLExpress01;AttachDbFilename=|DataDirectory|Database.mdf;Integrated Security=True;User Instance=True" providerName="System.Data.SqlClient" />

But it still Connection To The Database Failed,.

As you can see the only change is that I changed in the Data Source from SQLExpress to SQLExpress01 but I still get connection to the Database Failed.
Can somebody guide me in the right direction?

//Tony