Try the following steps to connect to your Micro:bit:

1. You may need to reload this page and try your program again.

2. Try disconnecting and reconnecting your Micro:bit. Then reload the page and run your program again.

3. If you are still having problems your Micro:bit may have an old firmware version that is incompatible with Codesters.
To update the firmware follow these instructions from Micro:bit

Update Firmware

Are you already running a Codesters project in another tab or window?

Micro:bit can only connect to one web page at a time. Try stopping other Codesters projects or closing other tabs or windows that may be using your Micro:bit.

If that doesn't fix the problem try disconnecting your Micro:bit, reloading this page, and reconnecting your Micro:bit.