You made too many purchases in a short amount of time. This will automatically trigger fraud and theft prevention. This can be done by the bank, VISA/MC/etc, PayPal or Epoch.
Epoch should know this.
I can not see who has this block active for you, if Epoch doesn't know then since you are using PayPal I'm guessing you have a bank or credit card linked to your PayPal and one of them did it. Also, Epoch should know this, their business is all about payments...
For future reference I suggest topping up your balance before making individual purchases. This will also give you 5% bonus on any deposits of $50 or more and it will speed up the checkout procedure significantly. It also enables you to make purchases from within the app.
You can top up your account balance by clicking on your username on the main SLR website in the top right corner. NOT your username here on the forum.