Hello,
Sorry to hear you are having issues.
It would be best to simplify your setup to help troubleshoot this.
Please try connecting your guitar (or another instrument) to input 1. Connect outputs 1-2 to your monitoring source. Do not make any other connections on the H90, and make sure no inserts are enabled.
Load up a preset such as Digital Delay “1.. and 2”. You should hear 2 distinct delay lines for the A and B voices. Turn the Delay Mix knob fully to A and you should only hear voice A out of 1 speaker. Turn Delay Mix fully to B and you should only hear voice B out of the other speaker.
Please carefully follow the above instructions and let me know what happens.