Trouble adding an m4r file under "Tones" in iTunes (using a Windows Computer)

Hi. I want to add a custom ringtone to my phone by adding it manually to Tones in iTunes while my phone is connected to the computer.

I've followed the typical procedure for this method in that I converted some MP3 files into AAC files. Then, I copied them into my file explorer and converted them from M4A files to M4R files.

Next, I connected my iPhone to the computer to sync with iTunes. But in dragging the M4R files into Tones (under my device) nothing really happens. You see an "uploading files" action happening above, but no file actually appears here. It doesn't appear in "Ringtones" on my phone either. It does the same thing when I copy-paste via keyboard shortcut (Ctrl C/V) and when manually pasting it in via the Edit tab.

Really weird it's not working because I had no problem with this years ago on an iPhone 4S. Appreciate any advice you may have here.

Other stuff: I know about the GarageBand method, but it clips the audio I have when putting it in; I'd like to have the full audio clip (39s). If anyone knows a way to do that, let me know. The ones I'm uploading above are ~20s each. From what I've done before and see on online guides, the max time allowable is 40s — not sure if this changed or not. But if it worked before for me, I don't see why that time allotment won't last now.