Why are my AirPods blinking amber after charging?

Have you followed. the instructions for setting up replacement AirPods?

1. In the setup animation, tap Connect, then tap Done. AirPods are ready for use.

Set up your replacement AirPods 4 (all models) or a replacement charging case

1. Put both AirPods in your charging case.
2. Connect the case to power, close the lid and wait 20 minutes.
3. Open the lid, then do one of the following:

• • If the status light flashes white, go to step 5.
  • If the status light doesn't flash white, continue to the next step.

1. Double-tap the front of the case while the status light is on, double-tap again when the status light flashes white, then double-tap a third time when the status light flashes faster. When the status light flashes amber then flashes white, proceed to the next step. If the status light still doesn't flash white, learn what to do. 
2. With the status light flashing white, close the lid of your charging case.
3. Before tapping Connect on the setup animation that appears on screen, go to Settings > Bluetooth, then do the following: 

• • If your AirPods appear in Settings > Bluetooth, tap the More Info button next to your AirPods, tap Forget This Device, then tap again to confirm. Continue to the next step. 
  • If your AirPods don't appear there, continue to the next step.

1. Open the lid, then go to the Home Screen on your iPhone or iPad. 

Set up your replacement AirPods or charging case - Apple Support