Bluetooth pairing fails, no more PIN entry field
I recently had a similar problem though different devices (Android Google Nexus 7 running Marshmallow and Motorola Buds Bluetooth headset). Turns out the headset needed a reset to forget all the devices it had learned. Since I switch between devices, I suspect my data in the headset itself had become corrupted. In any case this fixed my problem. You might try finding a headset reset for your device and see if that fixes your problem. You may also need to have your phone/tablet forget all the devices, too, as that has helped me in the past.