Have this excellent amplifier, enjoying the sound. I had 5.1 loudspeakers in Zone1, that were connected to Front L/R, Center, Sub and surround L/R connectors. Then I had Zone 3 connected to audio speakers in another zone via Presence connectors.

Recently I purchased another set of speakers for Zone 2. I had to then connect to Surround L/R connectors (as surround back connectors can't be used for Zone 2). I have reconnected my back spekers in 5.1 setup to surround back connectors. All Zones work as expected except 5.1 setup. There I do not get sound from surround back speakers. Following troubleshooting there might be three reasons:
1. Presence speakers are selected (not in my case, I says None in my set up)
2. Surround is set to None in speaker set. (This is correct, as I can't select either Large or Small, those options are grey)
3.Surround is set to None in speaker set (This is correct, as I can't select either Large or Small, those options are grey)

I understand I need to select either or both of above options, but how to do that. There is probably something I need to select somewhere else, to enable those options, but what and where....

Can you please help?