R6400v2 wont connect to mobile nighthawk app

I factory reset my router, plugged it into the modem via ethernet, and tried to set it up through the nighthawk app, although the network is up and I'm connected to it, the app wont connect to the router. All it says is "Issues connecting to 'network name'". I don't know how to proceed and connect it or troubleshoot it, there is no support or any real troubleshooting tips.