I have a Access 2007 app that's been used for years. 2007 mde front end & mdb back end, both on same PC. I use a Sagekey installer.
Over the last year, users started getting an error "undefined function 'nz' in expression". When you launch my app and click a couple buttons all is fine. Then click one button and "undefined function 'nz' in expression" message, rather than opening the screen it should. You have to quit the app and relaunch it. Usually the 2nd time you launch it all is fine. Quit and relaunch and you get the error again. So it's random. It happens on Windows 7 & 10 and on many PCs.
My App is written in VBA with dao recordsets. I used the Nz function all over the place. Never had a problem with it.
Surely the code is sound as it's worked flawlessly for many years.
Any ideas what causes this? Or how I can fix it?
Joe9