Your GA4 and Facebook data don't match because they track and credit sales with totally different rules. Each platform has its own attribution model and is blind to what happens on other channels, so you’re always comparing apples to oranges. This discrepancy is a common frustration, explored in episodes like "From Confusion To Clarity: How Ecommerce Brands Can Trust Their Data."
As Sam Piliero explains on the 2X eCommerce Podcast, Facebook's default setting is a "seven day click and a one day view." This means Facebook takes credit if someone just sees an ad and buys within a day, without even clicking. GA4 doesn't do that. Brendan Hughes drove this home on Honest Ecommerce when he noted that Facebook can't see the YouTube ad or email click that also influenced the purchase. Each platform wants all the credit which, as several hosts point out, leads to reporting more sales from ads than your store actually made. This is why more brands are adopting server-side tracking for a unified view.
Your first move should be inside Facebook Ads Manager. As Sam Piliero suggests, change your attribution setting from the default to just "7-day click." This shows you conversions coming directly from a click, giving you a much more conservative and actionable dataset to work from.