Update 2025:

When you have the same problem like me and you are using property sources with user managed identity the config should look like that:

spring:
  cloud:
    azure:
      keyvault:
        enabled: true
        secret:
          property-source-enabled: true
          property-sources[0]:
            endpoint: <your-key-vault-uri>
            credential:
              managed-identity-enabled: true
              client-id: <your-azure-client-id>

If your're using a system managed identity you can remove the client-id.