Issues with espruino+puck on old MacBookPro

Hi,

I have an old MBP (mid 2010), running MacOS 10.12.2. No native support for web bluetooth, but I got a USB dongle. This allows the Espruino IDE (running in Chrome) to display Web Bluetooth as an option when clicking on the top left Connect / Disconnect button.

The Puck shows up on the list of devices to pair with, but when clicking "Pair" it just remains in the same state: the "select a port" window displays the text "connecting" and the lower-left status bar displays "connecting to puck.js ####" (I've tried it with 2 pucks, always with the same results).

Here are the last few lines on the console:

Connecting...
Set Slow Write = true
Connecting to Puck.js 99f2
BT> Device Name: Puck.js 99f2
BT> Device ID: 6JLLdy4+yfbKuRbcKwaRNw==
(it stops here)

Any clue about what's going on?

Thanks!