fix apple pen connection problem

My steps to fix apple pen connection with iPadPro
1) make sure Applepen is completely recharged.
2) remove the old apple-pen link from iPadPro
3) turn iPadPro into airplane mode (this turns off Bluetooth by default)
4) Plug applePen into lighting bolt connection on iPadPro. This lead to paring message. Click pairing.

I then open up notes and activate ApplePen in smart-stylus setting. It worked.