Can't pay

I can't exchange Apex Coins. I have money in my Steam wallet, but even when I click the "Allow" button, no Apex Coins are added, and no money is subtracted from my Steam wallet. I've completed 89% of the 7th Anniversary event, but I can't make a purchase and can't get the final Super Legend shard. The event ends in two days, so I'd like to be able to make a purchase before then. Please help.