There are multiple solutions that could solve this issue: 1. Check whether the pressure sensitivity icon is activated (blue) next to the Radius and Strength settings. *Some brushes are purposely designed to not use pressure sensitivity | 2. Windows Ink can mess with your pen tablet. Check if Windows Ink is enabled and deactivate it. A quick Google search should be able to tell you where you find it. | 3. It could be an issue with your tablet or tablet software itself. Test if your pen pressure get's picked up at all or if the problem is only happening in Blender.

1. In your project file click: File > Append | 2. Open the "the_artists_essentials_texture_paint_brushes" Blender file | 3. Open the "Brush" folder | 4. Import all brushes that start with a three digit number (e.g. "013_basic_blade") | 5. Now you can choose the brushes in texture paint mode by clicking on the icon in the "Brushes" section of the Tool setting tab of the Property Editor (the sphere with scribbles on it) | *Brush Assets have been announced for Blender 4.3! So the way to import them will likely change for all 4.3+ versions. I will update this answer once I've updated the pack for these versions.

Texture painting in Blender can get laggy or even freeze for a couple of seconds when you're painting over a large area of pixels. Zooming in or using a lower texture resolution can avoid most lag.