Problem with languagesystem DFLT and latn

The first time I export the font, it show “languagesystem DFLT dflt;” in the feature.
When in Glyphs, all my .liga/ .end/ .init/ dlig work fine.
When I try to test my font in illustrator, those ligatures just won’t show up. (my open type setting is ON).
I can see my ligatures in illustrator’s glyphs panel, but when I click on them, nothing happen.

Tested in Photoshop, not working either.
Tried copy the ligature from Font book to Pages, not working.

I go back to my Glyphs file, change the “languagesystem DFLT dflt;” to “languagesystem latn dflt;”
export my font, test in illustrator and the ligatures/ end form works!!
but then I found some problems and need to edit my font. So I go back to the glyphs file (with languagesystem latn) to edit. Now I can’t access the ligatures even I have turn on the standard ligature in the preview.

So I changed the "languagesystem " back to “languagesystem DFLT dflt;” and the ligatures show back again in Glyphs again.
Is this normal? I should export my font with “languagesystem latn dflt;” but when I edit it, I should change it back to languagesystem DFLT dflt;?

Glyphs version: Glyhps 2.4.4
Mac OS Mojave: 10.14.1

What happens if you simply automate the languagesystems?

In which feature did you put the ligature code? The AI screenshot says salt, which would be a bad idea.

And are you using the Adobe Fonts folder?

Do you have any script/language tags in the feature code?

I’m resurrecting this old thread because I’ve encountered an issue with this as well.

I have a CP1252 font with a handwritten calt feature but everything else is generated automatically. In testing, the calt feature works fine in Word 2019, but when exporting a PDF or printing, none of the OT rules are applied.

After some extensive testing, I discovered that the lack of languagesystem latn dflt; was responsible for the OT feature failure.

Disabling the automatic generation feature and adding that languagesystem manually enabled everything to work correctly. Obviously this is some limitation with the older PDF / print feature in Word 2019.

I think that, therefore, if a font contains Latin glyphs, that the languagesystem latn dflt; needs to be added as in addition as DFLT is not sufficient.

So you mean that even if there are no latin specific substitutions, that line needs ot be added?

Yes, that appears to be the case.