When only 50 out of 6,000 products make it to Google Merchant Center after exporting from OpenCart, you know you have a problem.
After reading a lot of forum threads about why this OpenCart problem was happening, and after considering hiring someone to manually copy and paste it because the OpenCart module wasn’t working, I finally found the solution.
It looks like I messed up the product descriptions while exporting to Google Shopping.
After fixing the product descriptions, everything exporting correctly to Google Merchant Center!