Aha! Found this:
https://devialetchat.com/Thread-Remote-not-working
User Borgen posted how to reset a remote by holding down all 4 buttons for 2 seconds. I did that, then turned on only the Master (former Slave) to let it pair with that unit, then powered up the new Slave (former Master) 10 seconds later.
With a total trial time of 3 minutes so far, I finally have functioning dual-mono. Hopefully it continues to work this way! For what it's worth, I am still paired with SPDIF and I did not find success in changing the physical cable. It seems that dual mono D Premier is possible with SPDIF (and a bit of frustration).
Thanks to all for your help.
https://devialetchat.com/Thread-Remote-not-working
User Borgen posted how to reset a remote by holding down all 4 buttons for 2 seconds. I did that, then turned on only the Master (former Slave) to let it pair with that unit, then powered up the new Slave (former Master) 10 seconds later.
With a total trial time of 3 minutes so far, I finally have functioning dual-mono. Hopefully it continues to work this way! For what it's worth, I am still paired with SPDIF and I did not find success in changing the physical cable. It seems that dual mono D Premier is possible with SPDIF (and a bit of frustration).
Thanks to all for your help.