mcFUNCTION fails to summon armor stands

I have a command block with /function cosmo:prep which works fine but the summon armor_stand ~ ~3 ~ {Tags:[A],Invisible:1b,Invulnerable:1b} fails to summon the armor stand in. I did the command manually in spectator from the exact same location where the command block is and it works fine also that armor stand command also works fine when activated by a command block but doesnt work in mcfunction for some reason