About apple adapter

See the following from iPhone Repair - Official Apple Support

Apple accessories

Apple-branded accessories, including the power adapter, are covered by our warranty and consumer law. The Apple-branded accessories that come in the box with your product are also covered by your AppleCare+ plan. For details, contact your carrier, Apple, or an Apple Authorized Service Provider.

Read the Apple Limited Warranty for accessories

Contact Apple Support

If you bought it in February, it should still be under warranty. Contact Apple Support using the link at the top right of this page.

Or if you just want to purchase a replacement, see: Buy 20W USB-C Power Adapter - Apple

The power adapter? For what model of iPhone?

Is that the serial number for your iPhone? If so and if you have double-checked it and it isn't working, try another method of contacting Apple Support.

Use the serial number from your iPhone, not the adapter. You can get that at Settings > General > About > Serial Number.