Try using -SkipCertificateCheck

build/azure-pipelines.yml

@@ -167,24 +167,8 @@ stages:
                   inputs:
                       workingDir: src\Umbraco.Tests.AcceptanceTest
                       verbose: false
-                - task: PowerShell@1
+                - powershell: Invoke-WebRequest https://localhost:44331 -SkipCertificateCheck -TimeoutSec 120
                   displayName: Call website
-                  inputs:
-                      scriptType: inlineScript
-                      inlineScript: >
-                          add-type @"
-                              using System.Net;
-                              using System.Security.Cryptography.X509Certificates;
-                              public class TrustAllCertsPolicy : ICertificatePolicy {
-                                  public bool CheckValidationResult(
-                                      ServicePoint srvPoint, X509Certificate certificate,
-                                      WebRequest request, int certificateProblem) {
-                                      return true;
-                                  }
-                              }
-                          "@
-                          [System.Net.ServicePointManager]::CertificatePolicy = New-Object TrustAllCertsPolicy
-                          Invoke-WebRequest https://localhost:44331 -TimeoutSec 120
                 - task: Npm@1
                   displayName: npm run test (AcceptanceTest)
                   inputs: