Let's try using using REST API Method

Author: gep13

BuildScripts/default.ps1

@@ -264,7 +264,7 @@ Task -Name RunGitVersion -Depends __InstallGitVersion -Description "Execute the
       if(isAppVeyor) {
         Write-Host "Running on AppVeyor, so UpdateAssemblyInfo will be called."
         & $gitVersionExe /output buildserver /UpdateAssemblyInfo true
-        $script:version = [Environment]::GetEnvironmentVariable("GitVersion_LegacySemVerPadded", "Machine")
+        $script:version = $env:GitVersion_LegacySemVerPadded
       } else {
         $output = & $gitVersionExe
         $joined = $output -join "`n"