Subtitle Tag Question

I can't seem to get this to work so I'm resorting to asking for help!
I use HELIUM which writes standard tags (just about all of them). I have several files that I have indicated a SUBTITLE to. According to HELIUM that gets written to "tit3" tag.
When I open the files in MP3TAG editor that does not come across?
My goal was to edit the SUBTITLES in MP3TAG and have them import into HELIUM.

Can you advise on this, please?
Thank you kindly

Where did you look in MP3tag?
If you have not done that yet, then have a look at the extended tags dialogue (Alt-T) and see if the data is there.
If so, add a corresponding field in the tag panel or a column in the files list.

I've attached some screen shots to show you what I'm seeing. In the Extended Tag view there is no SUBTITLE but you'll see when you view the pics.
Thanks for your help!!Helium Entry Helium Tag Property MP3 Extended Tag View

the "00000 BPM" let me suspect that this is an MP4 file.
According to the list in

SUBTITLE (TIT3) has no match in MP4 files.