Hi @m-n-c-games,
Did you notice any error notification on your primary machine upon connection attempt?
Do you maybe have splashtop WiredX display on your primary machine? If yes, please uninstall the virtual display on it’s advanced settings.
For further analysis, could you please run dxdiag.exe on your primary machine, click “Save All Information”, then attach the output file (dxdiag.txt) on your next reply.