Merchant's tab upgrade isssue

I have a premium stash tab that I upgraded before the 0.3 patch, but I can't upgrade it to a merchant's tab. The upgrade button doesn't appear on the website. I'm currently playing the game on PS5.

If the tab is one of your original 4 free tabs (upgraded) or a quad tab, it will not be eligible for upgrade.

The premium tab will also have to have been purchased for your PS5 account.

Some users have had issues with sync between tab selection for PC and PS5, but it sounds like in your case your tab may not be eligible for the above reason.