Hi When I click on the alternate from the glyph panel or the menu and want to change the character for an alternate glyph (ex isolated, middle, initial or final position), the character stays the same because it detects there is no letter before and after, it is isolated and remains in the isolated form.
I can do it with Illustrator no problem but not with inDesign
Use "OpenType > Positional Forms" in the flyout menu in the Character panel to manually change this (see also the online help: Install and use fonts in InDesign).
(By the way: are you familiar with Arabic typesetting? It's quite uncommon to have to manually change the positional forms.)