Try remove netcore installer task
MODIFY
azure-pipelines-linux.yml
azure-pipelines-linux.yml
@@ -6,9 +6,6 @@ jobs:
pool:
vmImage: 'ubuntu-16.04'
steps:
- - task: DotNetCoreInstaller@0
- inputs:
- version: '2.2.101'
- task: DotNetCoreCLI@2
inputs:
command: build

MODIFY
azure-pipelines-osx.yml
azure-pipelines-osx.yml
@@ -6,9 +6,6 @@ jobs:
pool:
vmImage: 'macOS-10.13'
steps:
- - task: DotNetCoreInstaller@0
- inputs:
- version: '2.2.101'
- task: DotNetCoreCLI@2
inputs:
command: build

MODIFY
azure-pipelines-windows.yml
azure-pipelines-windows.yml
@@ -6,9 +6,6 @@ jobs:
pool:
vmImage: 'vs2017-win2016'
steps:
- - task: DotNetCoreInstaller@0
- inputs:
- version: '2.2.101'
- task: DotNetCoreCLI@2
inputs:
command: build

Try remove netcore installer task