This tutorial explains the difference between OFX file and QFX file. Quicken imports QFX files and does not import OFX files. Quicken set QFX file description as "Quicken OFX data" creating great confusion for its users that believe they need OFX files it import their data.
A confusion you may see when you work with a QFX file.
A OFX file has .ofx extension and the QFX file (Web Connect File) has .qfx extension.
Quicken marks them, when you install Quicken on your computer as Quicken OFX files.
So you can be easily confused, that the .qfx file is actually an OFX file, but it is not.
A QFX file is a Quicken Web Connect File, which Quicken calls Quicken OFX data file.
Quicken doesn't import OFX files, it imports only .qfx files, but calls them Quicken OFX files. So when you use a transaction file converter, for example, the ProperConvert app, and you convert CSV to QFX and you'll get the .qfx file, but you'll see in the file explorer, that it's called Quicken OFX data file,
if you have installed Quicken on your computer. Don't be confused by this description here.