This may sound simple, but the #1 thing you can and should do is create a series of marketing campaigns targeted only to churned customers.
You will get some back, especially if you have a High NPS in general and most of your customers like / love you.
Put together a drip-campaign that goes out every 60 days max (not too often), and also invite them to all new product release and similar webinars, and your customer events. That will keep you top enough of mind.
Does the SDR or AE reaching out to see if they can win back your business work? The hit rate is low, but this also works. Just don’t let them turn it into spam. But a human connection here, if it hits the lapsed customer at the right time, can work as well.
Whatever you do, create a dedicated marketing (and if you can sales) effort here. In the enterprise, it may even be 3–5 years until you get them back. So most importantly, go long. Structure the content, the meetings, the followups to assume it will take time.