I just deleted and recreated my Warlock and my Titan to make them both female, and my Arc and Solar supers aren't available on both characters. I went to Ikora Rey and bought everything for both Void supers and maxed those out, and it still doesn't let me equip or buy anything at Ikora for my Warlock and Titan Arc and Solar supers.
What I see at Ikora Rey: https://prnt.sc/4O_Fa-86OVwV
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You will need to complete the quests that unlock those subclass elements.