OpenType features for Armenian not working in PDF exported from MS Word

The features work correctly in MS Word, but upon export to pdf they fail. Analogical features for Latin and Cyrillic work correctly in the exported pdf file. The font file was crafted in FontForge, the pdf's were viewed in Chrome, Edge and Acrobat with the same results (except for blurry font rendering in Edge, lol). The script I used was as follows (excerpts):

languagesystem armn dflt;
languagesystem armn HYE;

lookup calt_armenian_Liwn {
    lookupflag 0;
        ignore sub uni053C' @arm_desc_left;
        sub uni053C' @armenian by uni053C.long;
} calt_armenian_Liwn;

feature calt {
script DFLT;
     language dflt ;
          lookup calt_armenian_Liwn;
script armn;
    language dflt;
          lookup calt_armenian_Liwn;
    language HYE;
          lookup calt_armenian_Liwn;
} calt;