Do weapons platforms need ordnance or supply?

I dont think so however just to be certain I do put suply pods on the designs as I have seen planets tiny ones I grant run out of suply in battle. Not all Mods allow them as components on weapon platforms Stock does I think as does the BM the IRM dosent

in combat they take supply from the planets supply... the planet always says "endless" in combat.

I dont thinkt hey need them.

They don't need supply. They have endless amount of it during combat, adding supply and ordnance to them is just wasting space.

IF you are playing in a Mod where Weap Platforms feature in ground combat then I believe you need supply and ordanance.

I think this is the most likly cause

Just a guess but ... if the WP can take part in ground combat, then it'll need ordnance and supplies for that combat. However, for the space battle, it won't.