Facebook requires a daily minimum spend of at least $1 (USD) per ad. If your currency is not set to USD in Facebook, your daily ad spend minimum will be equal to the exchange value between your currency and the US dollar.

For example: If you're budget is set to 50 in Marpipe, and you are using Canadian Dollars (~=.79 USD) in Facebook -> You must set your budget to at least 63.35 in order for your ads to deploy through Marpipe.