Visual Studio Team Services Release/Deploy fails - "No package found with specified pattern"

"More than one package matched with specified pattern. Please restrain the search patern [sic]." error usually occurs when 2 or more packages were found by the task since you entered "xxx\*.zip" in "Package or Folder" setting of the task. So you just need to update it to specify the detailed package name. Similar question here: Deploy azure website and webjobs in same sln using VSO - Error - There can be only one.

And for you original issue, you can also fix it by creating a new build definition with "Visual Studio" selected on "Build" tab and "Azure WebApp" selected on "Deployment" tab. This will create a build definition with required arugments added.

Had the same problem few hours ago. This how I was able to resolve the issue:

1. Ensure MSBuild arguments in Build solution step are: /p:DeployOnBuild=true /p:WebPublishMethod=Package /p:PackageAsSingleFile=true /p:SkipInvalidConfigurations=true /p:PackageLocation="$(build.artifactstagingdirectory)\"

2. Add step Azure App Service Deployment: ARM

3. Configure subscription and App Service Name
4. Package or Folder should be $(build.artifactstagingdirectory)\**\*.zip

Steps:

Azure App Service Deployment Configuration:

if you are using the default azure app service deployment task, add this to end of YAML file:

- task: DotNetCoreCLI@2
  displayName: 'dotnet publish $(buildConfiguration)'
  inputs:
    command: publish
    publishWebProjects: True
    arguments: '--configuration $(buildConfiguration) --output $(Build.ArtifactStagingDirectory)'
    zipAfterPublish: True

- task: PublishBuildArtifacts@1
  displayName: 'publish artifacts'

I had the same issue and this worked for me:

# ASP.NET Core
# Build and test ASP.NET Core projects targeting .NET Core.
# Add steps that run tests, create a NuGet package, deploy, and more:
# https://docs.microsoft.com/azure/devops/pipelines/languages/dotnet-core

trigger:
- master

pool:
  vmImage: 'ubuntu-latest'

variables:
  buildConfiguration: 'Release'

steps:
- script: dotnet build --configuration $(buildConfiguration)
  displayName: 'dotnet build $(buildConfiguration)'

- task: DotNetCoreCLI@2
  displayName: 'dotnet publish $(buildConfiguration)'
  inputs:
    command: publish
    publishWebProjects: True
    arguments: '--configuration $(buildConfiguration) --output $(Build.ArtifactStagingDirectory)'
    zipAfterPublish: True

- task: PublishBuildArtifacts@1
  displayName: 'publish artifacts'