Did you follow the Troubleshooting in the tutorial?
- From the Digitize->File->Edit settings (Figure 7), confirm the information in 's' matches your settings
- Confirm the information in 's' matches your COM port settings of your computer (this info is in the Device Manager)
- Press the button of the stylus, then execute s = instrfind() again. You should see that there are bytes available (94 bytes for Fastrak, 120 bytes for Patriot).
If you do not get #3, then you have communication issues. Check that the device is configured correctly.