There are many ways for the linkshim algorithm to detect bad links but the most commonly used are negative feedback (reports etc) and flagged content (string match, bad domain inside the link etc)
When it comes down to it a little deeper, fb will block with a certainty level. Let's assume you run baddomain1.com, it gets hard flagged, and your baddomain2.com loads a script or image from baddomain1.com, your baddomain2.com will automatically be flagged too.
Then domain age is very important. But like in your case, I haven't checked myself why it's not possible, just assuming now, age shouldn't be a problem and specially not the fact you run a shopify store.
One thing that's also very possible is if your campaign has been flagged, ads or pages related to it, then your domain will get flagged along with it, if they manually reviewed it.