Why won't my AirPods case turn on after charging?

hello, these past few days I’ve noticed that my airpod case won’t turn on, at first I assumed that it was dead and i needed to charge it, so I did, I left it charging for a whole day and when I tried using them the next day, fully charged, they wouldn’t turn on, I even tried holding down the back button to repair it to my phone but nothing works. Is this something I can fix myself or do I need to go buy new ones entirely?

[Re-Titled by Moderator]