In any event, the new devices will need to be set up as well as new or reconfigured activities to control them. The new activity setup will usually offer to use the soundbar for sound and then it should work as expected. Selecting the device used for changing channels should also be in the setup wizard. Checking the activity setup should start the setup wizard as well.
Using the TV remote to control the soundbar volume could work if CEC and ARC over HDMI are setup correctly and both components support it. I've always found CEC and ARC to be more of a nuisance due to incompatibilities and unwanted side effects when using activity based universal remotes.
I think the issue was using optical which doesn't go both ways
I've never heard of an optical cable that isn't bidirectional. Using the wrong connectors for audio in/out could cause issues but it sounds like the audio works, there just isn't any volume control.