For Chromebook Users on Chrome OS v133+ using Circuit Playground Express with Code.org Maker activities:
To use Maker activities, the Code.org Firmata application must be installed on the Circuit Playground Express. This is done by dragging the file onto the CPLAYBOOT drive, which appears in the Files app while the Circuit Playground is in bootloader mode. See https://studio.code.org/maker/setup. However, on Chrome OS v133 and above, the CPLAYBOOT drive no longer appears, preventing users from installing the necessary Firmata application directly from their Chromebook.
Workaround: Some users have successfully installed the Code.org Firmata by using a Windows or Mac computer to download and transfer the firmware to the board. Once installed, the board can still be used with Maker activities on the Chromebook. Unfortunately, this workaround does not work for all users.
We have reported this issue to the Google team, and we hope it will be resolved soon.