mm0398 Totally just fixed the issue. It's a Metamask settings issue. You have to reset your activity log in Metamask and then it will work and you'll be able to deposit DAI and then borrow alUSD from it. In Metamask go to: Settings, Advanced, Reset Account.
After that it'll work fine. The problem was that my deposit of DAI wasn't fully getting sent to Alchemix. Once you reset the Metamask settings, your deposit will go through, and you'll be able to borrow alUSD against it. Let me know if you have any questions.