App won't start

I have an computer training app I use on my ipad and iphone most every day and have never had a problem accessing my account. Yesterday I went to use it and it wouldn't let me log on either device. I have no problem logging into my account on their web site from my IMAC.

I restarted both devices and deleted the app and reinstalled it. Still no luck logging in. I called the software company and they were able to access my account and log in on the app with no problems from an ipad. We did troubleshooting and everything seems to be working fine from their end. I am able to log in through the app on my devices using other wifi accounts (apple store and starbucks) just not from my C3700/N600 router and Time Warner Cable.

TWC said the internet connection is good, I have no other problems with speed or conectivity. I can access all my other apps and the internet on my desktop computer and moble devices, just not this one app.

I also restarted my router by unplugging it, waiting a minute and plugging it back in, but that did not help. TWC suggested it might be an issue with port forwarding/triggering but I have no other problems with my router or internet and I am not sure why after using this app for 2 years, it would all of a sudden not let me log in.

I  checked the firmware on the router and it is up-to-date (V2.02.08) but I'm not sure what is causing this log in problem. I haven't made any changes to the settings since I'm not sure what to change but everything else has been eliminated except the router.

All my MAC OS software is also up-to-date on both devices (9.3.5)