When you receive a payment via PayPlug, the amount is immediately put on an isolated account. Thus, it isn't automatically transferred on your bank account.
In compliance with the French banking regulation, an isolated account allow that the amount you have on your PayPug account, not to be confused with other merchant's or Payplug's.
The money available on your PayPlug account doesn't "work" then, and remain yours, even when it isn't transferred on your bank account.
In order to receive the amount on your bank account, you should request a transfer, going in the "Transfers" menu of your PayPlug account and then clicking on "Transfer my balance".