Q: On I Pad Pro, can not use keyboard after it is fully charged.

Hi V.Flycatcher,

I understand that your keyboard is not working with your iPad Pro. If it is the Smart Keyboard, you can try a few things out like making sure the Keyboard and iPad Pro are in the Type position as well as restarting the iPad and keyboard. Take a look at the article below form more details. 

Use your Smart Keyboard with iPad Pro
https://support.apple.com/en-us/HT205237

Let me know if this helps. 

Have a good day