Hi rongon,
The green SDcard activity LED is solid on all this time.
This is normal with a Pi3 (for example see
here).
my RPi3 freezes at the screen where the arrows spin around and around in a circle
With screen you mean your Win10 PC, right?
What do you expect to happen? It is a web application and when the server is down the app also goes down.
If you select reboot the Pi should come back after a while. On some browsers you have to refresh the page.
Frank