I am not able to check it myself at the moment. But I would recommend you to attach a display and a keyboard to your server, also your USB with the OS.
When you restart the server it should tell you a way to stop the boot sequence and enter your BIOS. From the BIOS you can set the USB as your boot device and then restart the server again.
Now it should boot into the HexOS install sequence where it will reinstall everything from scratch, and you can decide whether or not you want to wipe your HDD/SSD pools.
I recommend you to get the newest HexOS ISO file and put that on your USB before you go through this process 🙂