I think it is because I have it at 100% off for corona virus sale. If you just choose Download or Claim > then select to "pay with paypal" with the value set to 0 USD, it should skip the payment and just add the game to your itch.io account. Let me know if it works or you still have issues getting it.
Hmm, I don't know then, must be something on itch.io end of things. I would ask the itch.io team directly for more info.
Everything in my control panels and my own testing says that pressing PayPal with 0.00 as the currency entered should be purchasing the game for your account.
For now you can just use the grey link on the pop up "no thanks just take me to the downloads". It won't claim the game, but should let you download it. Drake is one of my older games, so at this point any "update" will most likely be a sequel anyway.