Please follow the steps in the user manual at the "The device does not turn on" section: https://manuals.sharkrf.com/openspot4/en/troubleshooting.html#the-device-does-not-turn-on
If the recovery software does not see the device then please try using a different USB cable and USB port on your computer. If this does not even help then press and hold both buttons on the device at the same time for 10 seconds to enter it into bootloader mode before using the recovery software. Note that only the recovery software will be able to exit this bootloader mode so do not use this method otherwise.
After you've managed to power on the unit please upgrade to the latest beta firmware version. It has a fix for this issue.