In the import settings, either in the import dialog or the preferences dialog, see what you have for "treating raw and JPG as the same image".
Alternatively, there is an option in the Export dialog to automatically add the exported JPG to the catalog.
First in the Export dialog window there is an option to include the newly exported file in the catalog. That option should be checked. Next is your Sort Order If it is not set to Capture Time the newly exported image might be at the End of the film strip. So set the Sort Order to Capture Time.
Second there is also an option in the export dialog to Stack with the original. So if that option is checked any and all exported images will be right next to the original no matter what the file name is or how you have the Library/film strip sorted.
Thanks a lot.
Worked perfectly with the following change by me: Edit/Preferences/General/"Treat JPEG files next to raw files as separate photos"
The real issue turned out to be: Edit/Preferences/General/"Treat JPEG files next to raw files as separate photos"