Altium Unrouted Net in Fill
In my experience, Altium gets mixed up when vias are close together.  When it says there is an un-routed net from via to via, try moving the vias farther apart (or make them smaller).
You can also get more info about what Altium is thinking by going to Design -> Rules... and then select Electrical - Un-routed Net - UnroutedNet.  In that dialog box, uncheck the option for "Check for incomplete connections."  If that makes your errors go away, then it tells you that your vias are close enough that Altium thinks they should be connected together, but somehow doesn't understand that the polygon fill is making the connection.  Don't know why... seems like a bug to me.