Having issue with DNN 6 upgrade network path

So we are upgrading site and came across interesting problem. We have a 6.01 version we are using upgrade path upgrades. Going to 6.4 then 7 to 8 to 9 etc etc.

So far other version 7 sites upgrade fine, the version 6 sites as stated above fails. PLEASE NOTE: We CAN navigate to the site before moving upgrade files over and login as host, move around see the site etc, meaning the web.config database connectionstring is working. However once we move files over to upgrade and the upgrade wizard requires host login, hit next, it hangs and produces the "Network related error cannot connect to sql server blaa, blaa, blaa..."

Is there another area where the connection strig for the version 6 DNN is looking when upgrading other than the web.config? It's clear it's an issue with it can't find the SQL server, no that a login is wrong...

This is the error:

Line 215: Upgrade.Upgrade.UpgradeDNN(strProviderPath, DataProvider.Instance().GetVersion());

Win32Exception (0x80004005): The network path was not found [SqlException (0x80131904): A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found...

Possibly something with getting the path is wrong? string strProviderPath = DataProvider.Instance().GetProviderPath(); in the install.aspx.cs?

In case anyone else cares or needs this, in the DNN 6 version we had, way down in the web.config there is another "upgradeconnectionstring" that needs to match the main connection string. in our case the DNN WAS moved to a new server and the main connectionstrings were updated not the one below. All good now!

       add name="SqlDataProvider" type="DotNetNuke.Data.SqlDataProvider, DotNetNuke.SqlDataProvider" connectionStringName="SiteSqlServer" upgradeConnectionString="Data Source=YOURSERVER;Initial Catalog=YOURDNNDB;User ID=matchtomainuser;Password=matchtomainpassword;Application Name=DNNCore;" providerPath="~\Providers\DataProviders\SqlDataProvider\" objectQualifier="" databaseOwner="dbo"