I see you've posted this question on several other message boards...
You need to be more specific about how it's "not working". Because the system can still boot up and function without a CMOS battery - it just won't keep customized BIOS settings and/or time while the computer is off.
Does a 2032 not fit? Is it too large, too small? Not high enough? Too high?
Going by pics I found of that motherboard model #, it definitely looks like a CR2032 battery (though I can't confirm it is or not, as there weren't any pictures of the battery itself, nor could I find any documentation on what battery it used).
Having computer repair experience doesn't necessarily we have access to Acer's private service manuals.
Edit: did find a service manual for it:
However...no mention of model of battery anywhere in it. So looks like you're just going to either have to make sure that a 2032 indeed doesn't fit, or look through a list of other button batteries that may have the proper form factor that you need.