ESP/ESC switch apparently not working

The system may well be working in other ways but the operation of the switch is a different issue,apart from checking the switch ( when fitted) visual wise I’ve always checked to make sure the switch operated as it should.
Knowing Mercedes all there models work the same way.
Where possible check the owners manual and you’ll find the info below .

X To deactivate ESP®: press button : until the å ESP® OFF warning lamp lights up
in the instrument cluster.
The ÷OFF message appears in the multifunction display.
X To activate ESP®: briefly press button :. The å ESP® OFF warning lamp in the instrument cluster goes out. The ÷ ESP®ON message appears in the multifunction display.

It would be fail from me on this manufacturer but bear in mind operation of switch’s and mil are manufacture specific .

checking ESP/ESC switch operation for a few years now.. we still have advisories. These are very similar to minor defects but rather than a component already being defective, they indicate a component will become defective soon ..

so Electronic stability control warning lamp not working can not 'indicate a component will become defective soon'

fail using RfR 7.12(c) Other ESC component missing or damaged Major

I stand to be corrected by others with better knowledge/smaller hangovers....

A lot of older Mercedes don't put the ESP light on just a yellow warning triangle on dash, others don't have a switch and you have to scroll through Dash Menus to find it. They will usually display a message and still not illuminate the ESP light