bought a .2mm nozzle to try this week. both my Up Box+ and up mini 2 es i cannot change the nozzle diameter from anything but .4mm
Are your material profiles configured with the 0.2mm nozzle?
That should be the issue here. Check the material profile that was selected, when you change nozzle size in the menu.
You can add different nozzle sizes to your custom material profile easily.
If you get stuck with the settings, copy, or base some of your settings off the respective base Tiertime material.