Will pair with some devices but not all.

To truly understand the problem, and how to fix it, you should try and provide more information. Such as: which model of JBL Charge do you have? What devices are you having problems pairing to the speaker?

Moving on however, if some of the devices are not pairing, it could be a couple of things. Maybe the drivers are not updated? Good site on how to update

Also, you can try restarting the other devices, or even the speaker, to see if that would help with the connection.