Apex legends premium plus battle pass

I recently just passed tier 40 split one on the battle pass in Apex, saw the dope Loba skin on the ‘premium plus’ side and wanted to buy it. Though there’s no where for me to buy it that I can find. I earned the premium pass from the challenges in game and remember seeing I could upgrade it, but I hadn’t seen the loba skin so I wasn’t interested in spending the money on the upgrade at the time. Now I’m attempting to buy it but no where in the store or on the passes page does it show the ability to purchase the plus version of the pass. The passes screen only shows the plus items I “could” earn “more info” and “purchase levels” no where is there an ‘upgrade to plus’. Am I missing something? Or can you only purchase the plus version before or shortly after earning/buying the normal premium pass?