Hey, guys! I've got a very strange error when trying to connect two portals. 

When I press whatever 'connect portals' or 'test connection' buttons a red error appears sayin' "An unexpected Error has occurred while validating your request". Yikes!

So, I ensured the similar workflow is running on both sites. Next, I've done some debugging and discovered the malfunctioning method in

DotNetNuke.Enterprise.ContentStaging.StagingClientController.cs

public bool PingServer(string address, int portalId, Guid token) { /*====somecode====*/
client.PairService(request);
/*====somecode====*/
return true; }

So, the pair service. After some more advanced debugging I've found a root of evil:

The INSERT statement conflicted with the FOREIGN KEY constraint "FK_PortalSettings_Portals". The conflict occurred in database "MyDNNDatabase", table "dbo.Portals", column 'PortalID'. The statement has been terminated.
Gosh!

So, I've removed the specified constraint and saw a strange thing in my database. DNN tried to add another LocalServerToken with testing site ID though a targetServerAddress and TargetServerToken with Production site ID were expected to be added.

So, I've deleted a site and created a new one using the template. No luck as I expected.

THe last thing I did was manual adding a targetServerAddress & TargetServerToken in my database. The sites seemed to be connected but when I couldn't authenticate as Host and publishing content caused the same unexpected Error.

Anyone know the damn module so deep?