First, check if Blofeld is set to the MIDI Channel you’re sending data on. Press Shift+Global and turn the encoder a couple of clicks until you can see the Receive MIDI channel. Set the Receive MIDI channel value to the channel you’re sending data on or omni
Make sure that your Blofeld is connected to your computer directly and not through a hub.
Use the rear USB, not front USB connection.
Disconnect all other USB devices from your computer which aren’t needed at the moment.
Change the USB cable.
On Mac: Click on About this Mac in the Apple menu. Select System Report. Go to the Hardware dropdown menu on the left and unfold it. Select USB. Check if Blofeld is listed there.
On Windows: Press the Win key+R. Enter devmgmt.msc and press OK. Check if Blofeld is listed there. If Blofeld shows up as an “Unknown Device” and if there’s a black and yellow warning sign, deinstall the driver. Then unplug Blofeld, reboot your machine and plug Blofeld back in.
If this doesn’t work, switch your Blofeld on and off five times in a row. Don’t do this too fast, leave at least 1-2sec between switch operations.