Troubleshooting Guide: My .NET App Will Not Start Print

Quick Diagnosis Flowchart

Follow this decision tree to diagnose why your .NET Core application fails to start on Plesk Windows hosting.

Step 1: What Error Do You See?

Section A: HTTP 500.30

Most Common Causes:

1. Wrong .NET version selected
   • Fix: Plesk → Hosting Settings → Change .NET Core Version
2. Missing dependencies
   • Fix: Republish with all dependencies or use self-contained deployment
3. Database connection error
   • Fix: Check connection string, add TrustServerCertificate=True
4. Configuration error
   • Fix: Enable stdout logging, check logs for specific error

Section B: HTTP 502.5

Most Common Causes:

1. Application crashes immediately
   • Fix: Check stdout logs for exception details
2. Missing .NET runtime
   • Fix: Use self-contained deployment: dotnet publish -c Release --self-contained
3. Wrong startup DLL specified
   • Fix: Verify Application Startup File in Hosting Settings matches your DLL name

Section C: HTTP 500.35

Cause: Multiple .NET apps trying to run in same application pool with in-process hosting.

Fixes:

1. Change to out-of-process hosting in web.config:

   <aspNetCore hostingModel="outofprocess" ... />

2. Or use separate application pools for each app

Section D: Blank Page/Timeout

Diagnostic Steps:

1. Is the app pool running? → Recycle it in Plesk
2. Are all files uploaded? → Check httpdocs folder
3. Is stdout logging enabled? → Enable and check logs
4. Is the app listening on correct port? → Remove any hardcoded ports

Universal First Steps

1. Enable stdout logging:

   <aspNetCore stdoutLogEnabled="true" stdoutLogFile=".\logs\stdout" />

2. Create logs folder in httpdocs
3. Restart app and check logs
4. Verify Hosting Settings:
   • .NET Core Version matches your app
   • Application Startup File is correct (YourApp.dll)

Still Stuck?

Contact support with:

• Exact error message
• stdout log contents
• .NET version (8, 9, 10)
• App type (Web App, API, Blazor)