I don’t know if this will work for you, as I was missing a couple of issues you have such as the battery appearing empty and the light rail on the joycon not lighting up, but I had this issue too! Here's how I fixed it. My right blue joycon wouldn't work wirelessly but would work when connected to the switch undocked. So I went to the change grip/order tab under the controllers icon. I then held down the pairing button on the troubled joycon and it connected. Apologies if this doesn’t solve your issue.