Problem using Photoshop functions on Microsoft tablet while using finger as input

Hoping for some help here!

I have a Microsoft Surface, model 1824. I am trying to use the tools in photoshop such as lasso, paint (all the functions on the left-hand side tool bar) without a pen, just by touching the screen. I have the latest photoshop and my windows 10 is all up to date. 

I can use my finger to select file, edit, window - anything on the top toolbar but when it comes to actually editing these images the touch screen stops working. Does anyone know if you have to use a wireless pen for these to work or if there is a setting I need to enable?

I can use all of the draw, paint, cut functions in Illustrator with no issue. 

Any help appreciated, thank you. 

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