vb6 app will not launch

[jjsomer]

I have an app that is used on 50 machines. This app undergoes many revisions. My last compiled revision was implemented on all 50 machines. On 49 machines this revision works fine. On one machine, running the application results in an immediate shutdown. No error messages. It's as if the application never launched. Does anyone have any ideas as to what might cause this behavior?

[RhinoBull]

What's the difference between the previous and current revisions?
Did that machine (the one that doesn't work) get OS reinstalled, new anti virus, spyware, Windows Defender or perhaps firewall (local) activated? Many other questions may follow ...

[jjsomer]

Yeah, I figured a lot of questions would follow...

To my knowledge, the existing source code had one modification - to change the number of digits after the decimal point on a formatted value. Nothing new was added to the tester. The source was modified and compiled. I have tried cleaning the registry of all references to the app name. I have uninstalled and re-installed the app to try to revert back to the previous app version. I have tried moving the app to a different folder. Nothing seems to work. Although the app with the modifications can be executed from the VB6 environment - just not the compiled version. My suggestion was to reinstall the OS - but that is not the simplest task...

[Hack]

Does your application do anything to the registry?

In the Form_Load of your main screen, what code is being run?

Is the make, model configuration, software loaded, etc on this one machine totally identical to the other 49? If not, what is/are the differerence(s)?

[RhinoBull]

... I have uninstalled and re-installed the app to try to revert back to the previous app version. I have tried moving the app to a different folder. Nothing seems to work. Although the app with the modifications can be executed from the VB6 environment - just not the compiled version. My suggestion was to reinstall the OS - but that is not the simplest task...

That tells me that environment has changed - I would first check permissions. Your user may need to be local admin.
Also, re-installing entire OS is an exteme - I wasn't suggesting to do so, just checking whether or not it happened.
Without knowing specifics of your app it's quite difficult to suggest anything reasonable.