PayPal announced that they would be upgrading their IPN encryption to SHA-256. This change may affect any merchant that currently uses PayPal's IPN system. Primarily, this is a server issue. The question is does your host's server support SHA-256. Although, to ensure that our extensions fully comply with the new change, we have made recent updates to Nice PayPal Downloads and Nice Membership for Joomla.
More information regarding the PayPal upgrade can be found here PayPal Merchant Security System Upgrade Guide.