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 Mac

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. Click the wi-fi icon on your Mac and go to “Open Network Preferences” 
      2. Click the “Advanced” button
      3. Under the Wi-Fi tab, find and select AirYorkPLUS and click on the “-“ (minus sign) at the bottom of the list to remove it.
         1. Pro tip: if you have Wi-Fi info and AirYorkGUEST in the list, you should delete these as well for a cleaner interface.
   2.  Reconnect to AirYorkPlus in the dropdown menu next to “Network Name”
      1. Enter your Passport York credentials to authenticate to the Wi-Fi
         1. 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/