The plot method of alphaShape objects does not accept an axes handle as its first input. Instead you'll need to specify the uiaxes handle as the value for the 'Parent' property of the patch that the plot method of alphaShape will return. First make some data and use that to create an alphaShape.
x = rand(10,1);
y = rand(10,1);
shape = alphaShape(x,y);
Now as part of this example I create a uiaxes, but you have a uiaxes in your app that you can use instead.
ax = uiaxes;
Finally plot the shape.
plot(shape, 'Parent', ax)
