Roku Ultra surround lost until factory reset
You need to verify that you have Volume Modes disabled (these disable multichannel audio).
These are often enabled by default for many firmware versions/builds, so a Factory Reset may re-enable them if you previously disabled them. To make matters worse these audio settings are "hidden" and only available during playback.
To disable Volume Modes for your 4660:
1) During playback (of any video) press remote Options (*)/Volume mode = Off
Otherwise your audio-related settings should be configured as follows:
1) Settings/Audio/Audio mode = Auto
2) Settings/Audio/Preferred Streaming format = Auto
3) Settings/Audio/Digital output format = Auto
Note: If your connected device only supports DD/AC3 (and not DD+/EAC3), you will be limited to stereo audio in many apps/services that ONLY use DD+ (e.g. NetFlix, Prime, Disney+, Max, Peacock).
You can check for DD+ support if you HIGHLIGHT Settings/Audio/Digital output format = Auto - you should see DD+/Dolby Digital+/Dolby Atmos listed as Available for full 5.1 support in all apps/services.
