Quite a lot of people seem to have trouble connecting to the Vixen mounts, a search for “vixen” will show some information.
One thing could be that the Vixen takes a long time to connect to the mount, possibly longer than SGP is allowing.
One thing that might help to find out what is happening is to run the ASCOM Conform tool on the Vixen and post the log it generates. Conform can be downloaded from the ASCOM site, in the developer section I think.
At least try to connect through another application such as Cartes du Ceil.
Another possibility is to connect through the ASCOM POTH telescope hub. I suggested this a few days ago but haven’t heard any more. Often that means that it worked.