Add to Cart Error

I followed the instructions and got the sync to work. My products have variants. But when I select a variant, I get this error:

Error: Selected option(s) aren’t available. Please select a different combination. (wps_get_variant_id)

I didn’t see any other info on how to setup the Buy Button functionality or anything like that. I’ve read through all your documentation. Any help would be greatly appreciated!

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