What you’re seeing is a relatively new process Amazon has been rolling out where newly created ASINs are automatically held for “compliance checks” before they go live, especially when GTIN exemptions are involved.
Even though your products are just standard cotton/poly shirts, Amazon’s systems sometimes flag new listings for review to confirm they don’t fall under restricted product categories (chemical content, textiles requiring certification, children’s clothing safety standards, etc.) or that they aren’t violating brand/trademark rules.
In most cases this review is automated but can take anywhere from a few hours up to several days, and occasionally longer if the ASINs get routed to a human compliance team. They may be verifying things like textile labeling requirements (e.g. fiber content disclosure under EU/US textile regulations), children’s product safety (if Amazon’s bots think it could be kids’ apparel), or confirming that the GTIN exemption and brand details match your account history.
Many sellers report the listings eventually clearing on their own without any action needed, but if they remain suppressed for more than a week it’s worth opening a case with Seller Support under “Listing blocked or removed” and attaching your brand authorization or textile compliance info if available.