If you are able to find a SKU by searching for it directly, but don't get any results when searching for the ASIN, it's likely that the ASIN isn't associated with the Master Listing.
When searching in the Manage Listings page, you are searching the Master Listing which is created when the listing is first created or imported into Listing Mirror. Typically, if you have a listing imported or created first for Amazon, that ASIN is associated immediately, because it's a required field for Amazon. However, if you imported a listing from a non-Amazon marketplace, it's likely the ASIN didn't get associated with the Master Listing, which is why you aren't able to search by ASIN and come up with a result! Luckily, fixing this issue is very simple! All you need to do is find the Master Listing in the manage listings page, you can do this by searching for the Master SKU and clicking on the cog wheel underneath the title:
Add the ASIN in the ASIN field and click save changes:
Then you should be able to search and find the listing with your ASIN!
If you have any issues with your search function, please reach out to support.