Hazmat reviews are generated directly from Amazon and, unfortunately, we have no control over this besides displaying the error when they send it over.
While you may see the item available on Amazon as a Merchant Fulfilled item, this error indicates Amazon is not currently allowing the item to be listed as an FBA item until they have finished reviewing it to see how it should be classified.
Once the Hazmat review is lifted, Amazon will send the update through the Selling Partner API (SP-API) and this should resolve the error in Stratify.
We suggest opening a case with Seller Support if you have questions as to why the restriction is being placed on a specific ASIN. You can also check their help article for more information on the review process- Dangerous goods review process (hazmat)
There is a Lookup an ASIN tool on the page linked above that can be used to check the classification status of the ASIN for FBA as well.