The Switch 7 BE straight up doesn't come with a driver for it's Wacom EMR stylus input, a very coveted feature that is advertised everywhere for this tablet. The oversight not only makes the pen lack configuration options (pressure sensitivity, etc) but the button on the pen barrel does absolutely nothing. This holds true for third party pens used on the Switch as well (and of course, the acer pen and its button work just fine when you use it on your competitions devices, like the Samsung tablets, and the HP Zbook).
I've confirmed this issue with multiple owners, and support channels have been a dead end. I've had to create an app that intercepts HID input and translates it as a work around, which is a bit ridiculous just to get a button Acer put on its own hardware working. It would probably be a good idea to support your new devices.