Unfortunately, phone screens are sensitive to impact damage and a drop can easily break loose the delicate connections between the glass the screen circuits are printed on and the flex cable going to the motherboard. You wouldn't necessarily see any physical signs such as cracked glass, but your symptoms are indicative of a damaged display.
Sorry to say, those connections aren't repairable, so the only fix would be to replace the screen (again). On some phones it's possible for a drop to knock the display connector loose from its socket, but on Apple phones all connectors are screwed down with metal brackets, making it impossible for them to come loose. The only possibility I see here would be if the repair shop neglected to replace the display connector bracket, allowing it to come off, but that's not a likely scenario. The only way to check that is to open up the screen and verify that the metal bracket is in place.
Otherwise I strongly suspect you're now in the market for another screen. Assuming your repair shop used an aftermarket screen, you should have seen a warning that the phone couldn't determine that your display was an original Apple part. If that's the case, it's possible the screen they used wasn't as robust as an Apple factory part and could be more easily damaged by a drop than an Apple display would be; with aftermarket screens it's a bit of a crapshoot as to whether you're getting a quality part or not.
It would be worth your time to contact the repair shop and see what they say, but most shops won't cover physical damage such as drops under warranty.
Should you decide you want to take charge of your repair yourself, you can use the iFixit Screen Replacement guide to install a new screen yourself.
iPhone 14 Screen Replacement - iFixit Repair Guide
This way you get to choose what screen to put on; you can buy a high quality aftermarket screen here on iFixit, or you can go online to either the Apple Self Service Repair Store to get a new display, or eBay where you can find used screens, many in perfect condition, to get a genuine Apple screen. For an OEM screen, once you've installed the it, if you update to iOS 18 or later you can use the new Repair Assistant to pair the screen to your phone and restore True Tone and automatic brightness settings and eliminate the warning messages.
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