I have copied a couple of resources below that should help you install your new ad tags!
If you have completed all of these steps correctly and the ads are still not firing, implementation may not be the issue. Whether or not an ad unit fires an impression depends on multiple factors, however. The domain in question has to be approved into the sovrn exchange and the tags need to be properly aligned to our demand and buying partners. Where sovrn is placed in the ad stack, the kind and amount of traffic visiting the site, price floors, and ad unit placement on the page also impact the overall fill rate of a tag.
If you could reach out to us directly at email@example.com with your Meridian username we would love to take a closer look at your account.