They haven't updated the plugin since they first released it (2015), I don't think it would be a good idea to use it. Here are some good alternatives:
 
OpenNode: https://help.opennode.com/en/articles/2564096-how-to-setup-opennode-on-opencart
Coinbase Commerce: https://github.com/coinbase/coinbase-commerce-opencart
CoinGate (If interested in accepting alts): https://www.opencart.com/index.php?route=marketplace/extension/info&extension_id=22958