When Photoshop is opened from your Mac, you're not able to draw?
What happens when you try drawing in Photoshop? Does anything show on screen instead?
Even though Astropad mirrors, it doesn't adjust to the screen aspect ratios or resolution.
We are looking into a workaround, but it will take time.
You can use "Move & Zoom" to resize and zoom in for your iPad screen.
On your iPad, when you hold the white ring button on screen,
it will bring you into "Move and Zoom" mode
that allows you to pan and adjust the size of your screen with two finger gestures.
When you tap the white ring, it opens the sidebar shortcuts.
At the bottom of the sidebar, you can switch from "Draw" to "Move & Zoom",
and adjust the screen size from there as well.