Since the release of Routeros 6.39, the P2P feature has been removed from the mangle & firewall rules. Therefore, the only way to filter BitTorrent traffic now is to use the layer7 protocol. The code below along with the firewall filter rule will allow you to identify users who are BitTorrenting on you network.
You have upgraded to RouterOs 6.39.x and now your P2P mangle rules are no longer working. This issue is caused by MikroTik removing the P2P option/field from the mangle rules. There explanation is that this method of matching P2P traffic is obsolete. The image above shows what the error looks like. To fix this