Can I use SharpCap Polar Alignment if I cannot see Polaris?

No. The polar alignment routine in SharpCap Pro requires a view around the celestial pole to work correctly. SharpCap Pro has a built-in plate solving tool to perform polar alignment – this works if you are pointing with 5-6 degrees of the celestial pole. If trees or buildings block your view of this area of the sky then you can’t use SharpCap for Polar Alignment.