PGAdmin will not start on Windows 2022 server and Windows 2025 server builds.

[AldoRET]

We are currently rolling out new stepping stone servers with 64-bit versions of Windows 2022 server and Windows 2025 server, but PGAdmin4 will not start on these builds.
Our current stepping stone servers are running Windows 2019 server and PGAdmin4 v9.14, without problems.

We have tried to install and run (with admin rights) several different versions (v9.15,v9.14, v8.14) on the 2022/2025 builds but none of them wil start up.
Attemps to run with it with a disabled local windows firewall, disables virus software and without a Palo Alto Terminal Agent have had no success.

Deleting the pgadmin4.db file before startup did not help and the pgadmin4.log file only gives the following:

2026-05-26 09:28:24,259: WARNING werkzeug: Werkzeug appears to be used in a production deployment. Consider switching to a production web server instead.

What I get is the following fatal error during startup:

The pgAdmin 4 server could not be contacted:

pgAdmin Runtime Environment

Python Path: "C:\Program Files\pgAdmin 4\python\python.exe"
Runtime Config File: "C:\Users%UserName%\AppData\Roaming\pgadmin4\config.json"
Webapp Path: "C:\Program Files\pgAdmin 4\web\pgAdmin4.py"
pgAdmin Command: "C:\Program Files\pgAdmin 4\python\python.exe -s C:\Program Files\pgAdmin 4\web\pgAdmin4.py"
Environment:

• ALLUSERSPROFILE: C:\ProgramData
• APPDATA: C:\Users\%UserName%\AppData\Roaming
• CLIENTNAME: %ClientName%
• CommonProgramFiles: C:\Program Files\Common Files
• CommonProgramFiles(x86): C:\Program Files (x86)\Common Files
• CommonProgramW6432: C:\Program Files\Common Files
• COMPUTERNAME: %ComputerName%
• ComSpec: C:\WINDOWS\system32\cmd.exe
• DriverData: C:\Windows\System32\Drivers\DriverData
• EFC_9108_1592913036: 1
• EFC_9108_2283032206: 0
• ELECTRON_ENABLE_SECURITY_WARNINGS: false
• HOMEDRIVE: C:
• HOMEPATH: \Users\%UserName%
• LOCALAPPDATA: C:\Users\%UserName%\AppData\Local
• LOGONSERVER: %DCName%
• OS: Windows_NT
• Path: C:\Program Files\pgAdmin 4\runtime;C:\WINDOWS\system32;C:\WINDOWS;C:\WINDOWS\System32\Wbem;C:\WINDOWS\System32\WindowsPowerShell\v1.0;C:\WINDOWS\System32\OpenSSH;C:\Users\%UserName%\AppData\Local\Microsoft\WindowsApps;
• PATHEXT: .COM;.EXE;.BAT;.CMD;.VBS;.VBE;.JS;.JSE;.WSF;.WSH;.MSC
• PGADMIN_INT_KEY: b6725818-44b5-4e9f-abc8-3a8951ff1999
• PGADMIN_INT_PORT: 24158
• PGADMIN_SERVER_MODE: OFF
• PROCESSOR_ARCHITECTURE: AMD64
• PROCESSOR_IDENTIFIER: Intel64 Family 6 Model 79 Stepping 0, GenuineIntel
• PROCESSOR_LEVEL: 6
• PROCESSOR_REVISION: 4f00
• ProgramData: C:\ProgramData
• ProgramFiles: C:\Program Files
• ProgramFiles(x86): C:\Program Files (x86)
• ProgramW6432: C:\Program Files
• PSModulePath: C:\Program Files\WindowsPowerShell\Modules;C:\WINDOWS\system32\WindowsPowerShell\v1.0\Modules
• PUBLIC: C:\Users\Public
• PYTHONDONTWRITEBYTECODE: 1
• SESSIONNAME: RDP-Tcp#0
• SystemDrive: C:
• SystemRoot: C:\WINDOWS
• TEMP: C:\Users\%UserName%\AppData\Local\Temp\16
• TMP: C:\Users\%UserName%\AppData\Local\Temp\16
• USERDNSDOMAIN: %DomainName%
• USERDOMAIN: %Domain%
• USERDOMAIN_ROAMINGPROFILE: %NAME%
• USERNAME: %UserName%
• USERPROFILE: C:\Users\%UserName%
• windir: C:\WINDOWS

---

Total spawn time to start the pgAdmin4 server: 0.014 Sec
2026-05-26 09:28:24,259: WARNING werkzeug: Werkzeug appears to be used in a production deployment. Consider switching to a production web server instead.

• Serving Flask app 'pgadmin'
• Debug mode: off

I also monitored the startup proces with Process Monitor v4.02, and did notice a lot of entries of the pgAdmin4.exe with name not found entries for registry keys, but am not able to determine which are relevant (and there are a lot of them).
I also noticed several entries for CreateFileMapping events with the FILE LOCKED WITH ONLY READERS result.

I would appreciate some help, because right now I am not able to get it working properly, and am at a complete loss on how to resolve the issues.

Kind Regards,

Aldo