Could you provide more details of exactly what this means? Are you suggesting they combined the total weight of your checked luggage and your carry-on bags to compare against some value?

As others suggest after your post, I have never had Copa weigh my carry-on bag, ever, in 10+ years of frequent flying. On very rare occasions, they have asked to allow them to attach a "carry-on bag" ribbon to my rollaboard. But certainly never weighed, or performed any sort of calculation for a combined total weight. And that includes some trips with my family, with numerous bags.

As far as the rest of this thread goes, lack of specificity, contradicting responses from Copa, agent capriciousness, general uncertainty, varied unexplained results, all are normal.