Here’s what the error may look like:

Clicking into the Etherscan link, you should see:

When you are buying a Set, we need to convert the currency you are using to buy the Set (default set to ETH, but can be changed by clicking the dropdown arrow) into the necessary components of the Set in order to collateralize the Vault that then mints your token. For example, if you are buying a WBTC:cUSDC, and pay with ETH, we need to convert your ETH into WBTC and cUSDC in order to mint you a token representing your deposit. To do this, we use two decentralized exchanges, Kyber Network and 0x protocol to make sure you get the best price.

When you input a quantity on the buy screen we broadcast it to both decentralized exchanges in order to get the conversion rates. Then, we automatically pick the best one and prepare the order for when you are ready to execute the transaction.

The most common reason for the “ORDER_UNFILLABLE” error is when the best rate is provided by 0x. The rates 0x provides expire within 5 minutes so that means if it takes you longer than 5 minutes to execute the transaction, and for the transaction to be mined, the 0x rates will have expired and you will get the “ORDER_UNFILLABLE” error. This can either be because you took too long to hit “Submit Buy” or the gas costs were not high enough to enable a quick transaction.

The solution is simple, click out of the “Buy” window and try again. If you are manually editing the gas costs for the transaction, consider leaving it closer to the default. The amount we preset is optimized to execute the transaction as fast as possible. You should be able to proceed without an issue.