Failed to download or parse release-index.json with error:

My Azure Devops build has started failing with the following message in the log

Starting: Use .NET Core sdk
==============================================================================
Task         : Use .NET Core
Description  : Acquires a specific version of the .NET Core SDK from the internet or the local cache and adds it to the PATH. Use this task to change the version of .NET Core used in subsequent tasks. Additionally provides proxy support.
Version      : 2.165.0
Author       : Microsoft Corporation
Help         : https://aka.ms/AA4xgy0
==============================================================================
Tool to install: .NET Core sdk version 3.x.
##[error]Failed to download or parse release-index.json with error: {}
Finishing: Use .NET Core sdk

The YAML contains

steps:
- task: UseDotNet@2
  displayName: 'Use .NET Core sdk'
  inputs:
    packageType: 'sdk'
    version: 3.x

the image is windows-2019