API Request Failed What does this phrase mean and how do I fix it?

I used Cloud Flare’s DNS service well until a few hours ago.
However, about 30 minutes ago, the error “API Request Failed: GET /api/v4/accounts/e5a2ef06062/registrar/domains/example.com (503)” has occurred.
What is this error and how do I fix it?!

That looks like a temporary glitch. If it doesn’t clear up, open a ticket:

To contact Cloudflare Customer Support, login & go to https://dash.cloudflare.com/?account=support and select get more help. If you receive an automatic response that does not help you, please reply and indicate you need more help.