Thanks all for the tips. For the benefit of anyone searching with the terms I used above, as I couldn't find this reference, here is a restatement:
"Issue: Not all notes, folders, or tags are displayed on the mobile app🔗
Response: Joplin does not have a background sync on mobile devices. When Joplin is closed, sent to the background or the device is put into sleep (display off), the sync is interrupted."
Samsung Galaxy's come with a max screen timeout setting of 10 minutes, which was too short to maintain focus to tap on the screen to keep the sync going. 3rd party apps such as caffeine were not effective for me in keeping the screen on.
Once the sync stopped at a partial point, I was not able to populate more than the initial sync no matter how many tries, without uninstalling the app and re-downloading and reinstalling, then adding in my Dropbox (sync target) again.
Placing the Samsung in development mode, there is an option to keep the screen on indefinitely if plugged in. Once this was enabled, the initial sync fully completed and all is well.
Development mode is found under "Settings", "About Phone", "Software Information", and then enabled by tapping the "Build Number" 7 times.
Once in development mode under the "Settings" and next to/after "About Phone" is a new "Developer Options" heading. The indefinite screen time out can be found by searching and toggling to be on when plugged in.
A side note, I did toggle off the "Fail Safe" under the Joplin app configuration settings for the initial sync, and have now changed it back. Not certain if this was helpful or needed.
Thanks to the community for the response.