I have the same problem.
If the volume is changed with the rotary encoder you can’t see the change in jivelite and also not on my squeezeplayer remote app using my mobile phone (but in the app I an see the changes I make in jivelite using the touch-volume-bar).
But all methods of changing the volume (jivelite, app, rotary encoder) you can see in the IQAudio settings tab (Settings for Master Volume)…
In addition the percentage value in the settings tab isn’t the same like my app shows me.
…and the volume control of jivelite seems to be not linear. Very confusing 😉
Maybe this it a side effect of this strange failure:
Turning the rotary encoder only one icrement („click“) will change the volume by 10 percent.
Can you maybe add a settings value we can change within the webinterface to change the size of volume-steps when turning the encoder one „click“?