You've possibly changed the MIDI channel configuration from Streichfett and/or the attached MIDI devices.
Switch on Streichfett and wait a few seconds.
Press and hold all four Memory buttons until all 4 LEDs start to glow. While holding them down, play a note to Streichfett via MIDI on the channel that Streichfett should be adjusted to receive notes on. In case any MIDI channel from 1 to 14 is selected, the Solo section can be triggered independently of the Strings section on the next channel, with split settings being ignored. So in order to e.g. play Strings on MIDI channel 1 and Solo on MIDI channel 2, proceed as follows:
• Press and hold all four Memory buttons and play any key on your master keyboard on MIDI channel 1 to set the MIDI channel.
• Set Balance to the middle position so you can hear both Strings and Solo.
• Press and hold the lowest key on your MIDI master keyboard and select "Low" with the Split switch. This sets the split key very low and prevents Solo to be heard, if you play Strings on MIDI channel 1.
Now you can play Strings on MIDI channel 1 and Solo on MIDI channel 2.
Please set the MIDI channels new on your Streichfett as described above and retry.