I presume this is a cranks ok but won’t start and run problem. You hear that rrr rrr rrr sound w/the key in start, right?
The first step as mentioned above is to discover if the problem is either no spark, or no fuel. It is usually one or the other. Spark is usually the easiest of those. Ask your shop to show you how. You’ll need a helper to turn the key to “start” while you check for a spark at a spark plug. Easiest to do using a spark sparkplug.
If you don’t want to do this yourself, ask the shop to keep the car until they’ve discovered themselves the problem is spark or fuel. It may take a few days or even a few weeks.
The relay mentioned above by Tester has been a common complaint w/Honda Civic owners here. I don’t recall hearing this as much now as some years ago however. If that relay fails I think the symptom is there’s neither spark nor fuel. You can use the forum search feature (icon above, right this page) to see what other Honda owners done.