It sounds like we may have missed a step somewhere in the update process so let's go through that here and see if we can figure it out:
1. download the newest FW here:
https://conductivelabs.com/forum/attachment.php?aid=290
be sure to save it somewhere like the desktop where it's easy to find.
2. Open the teensy loader (I'm assuming you've already downloaded this for your computing platform of choice), and drag the fw file (it should have a .HEX extension) onto the loader. It will now be listed across the bottom of the loader window.
3. Connect the MRCC to the computer via the PC USB port, not the USB C power socket on the side of the device.
4. On the teensy app, press the Auto button
5. Press the FW button on the MRCC with a pencil or something small and pointy
6. The loader should flash the FW in seconds, and the MRCC should power up.
If the MRCC hangs up on rebooting then power cycle it while holding down the green button to factory reset it and see if that solves the issue. If you continue to have issues, please reach out to me via email at Support@conductivelabs.com and I will help you trouble shoot further.