First, try these general troubleshooting steps found at the link below:

https://ithelp.glendon.yorku.ca/faq/index.php?action=artikel&cat=26&id=79&artlang=en&highlight=airyorkplus

I've checked and my account works but I  still can't connect on my iOS Device

Potential Problem: I was connected just fine recently but now I can’t connect. / I changed my password recently and now I can’t get internet on AirYorkPLUS 

1. Answer: Try resetting your connection on AirYorkPLUS by deleting and re-adding the network.
   1. To forget the network follow these steps:
      1. Open Settings on your device
      2. Enter the Wi-Fi settings
         1. Select AirYorkPLUS
         2. Select “Forget this network” and confirm by clicking “Forget” on the pop-up window
            1. Pro tip: if you have Wi-Fi info and AirYorkGUEST in the list, you should delete these as well for a cleaner interface.
         3. Reconnect to AirYorkPLUS by selecting it in the network list on your iOS device
            1. Enter your Passport York credentials to authenticate to the Wi-Fi and click “Join”
            2. Should a pop-up appear about verifying the certificate, click on “Trust” or “Continue” depending on the option presented.
               

 If you are still unable to connect, fill out the AirYorkPLUS problem report form found at the following link:
https://www.glendon.yorku.ca/its/ppy/help-resources/forms/glendon-airyorkplus-request/