Help Conversions API not showing when selecting purchase as a conversion event.

I want to launch some instagram ads but when selecting my conversion event, only page view has a green box next to it saying conversions API. I want to select purchase as my conversion event. I ran an ad before this which got 2 sales but didn’t show on the ad analytics. I believe it’s because the conversions api box doesn’t show up next to purchase when I select the conversion event. I know my conversions api is set up properly because the event manager does show the 2 purchases I mentioned but doesn’t attribute them to the ad. Is there a way to fix this?