null window error on SubVI

[MTHPCB]

I received this error on an application:

It comes when the subVI verifylength.vi is called. I searched the forums and I saw to check and make sure that the remove front panel option is deselected in the build settings, and also to make sure that the show front panel option is selected in the subvi setup and the VI's properties. All of those were already setup properly, but I am still receiving this error.

Any thoughts on what else may be causing this problem? The error shows itself when a user is prompted with a three button dialog and depending on which selection a different subVI opens. The other subVI works fine, it is only this one. I have verified that the settings are the same between the two and I am still getting the error.

[MTHPCB]

I looked at this code again this morning. I added an explicit call to open the front panel and then close it later and that seems to have worked. I am still not certain why that works, because I have a second VI that I do not explicitly say to open the front panel and it works.

[JoshY]

Hi MTHPCB,

Glad you got this figured out! What do those two subVIs do differently? If you'd like to continue troubleshooting this, you may also want to try switching which button opens which VI or try opening a different subVI.