If you are using Simple Google Analytics then the ecommerce tracking is built in so it won't be a "module based" problem (even the earlier versions should allow ecom tracking).
The likely cause is on the Google end or in the tracking code you chose.
Make sure you setup ecommerce tracking within your Google Account for the proper "tracking id" (if you have multiple ones).
The other thing you may want to try is to switch to the legacy tracking code (done from within the admin configuration of zen cart) to see if that works. Both tracking options should be ok, but we're trying to eliminate possible causes here.
See if any of those help.
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