Amazon discontinued the old Kindle for PC app on June 30, 2026, and replaced it with a new Kindle for Windows app available through the Microsoft Store. However, the new app does not currently support Windows on ARM devices. So, if your Surface Pro uses a Qualcomm Snapdragon processor—as many of the newer Surface Pro models do—you may find that the Microsoft Store won't let you install the app, or it may simply fail to work properly after installation. This explains why everything you've tried so far has been unsuccessful, even though it seemed like it should have worked.
Use Kindle Cloud Reader in a web browser if your textbooks support it.