In my experience, one can is sometimes not enough to get the compressor to kick on. Also, Mercedes tend to fill very slowly for some reason. I'd try another can and if it doesn't kick on then, I'd manually kick the compressor on.

It should be noted that if weather is mild, that will make the car fill slower. You can also put the can in a bucket of hot or warm water to speed things up.

edit: 110 sounds high for low side pressure. This sounds stupid but are you sure that the fill valve is not stuck? I have had that happen before.