I created an server side application which is generating PkPass files using Apple WWDRCA and Pass Type ID cert. My certificates are installed on the server and they are valid until end of 2017 but my Apple Developer account will expire in a few days. I'm wondering will my application continue to work without any issues or I will need to renew my subscription.
You will continue to be able to issue and update passes until your certificate expires. However, we have experienced problems with clients who have let their developer account lapse and have subsequently lost the PassTypeID.
If you anticipate the need to issue or update these particular passes after the expiry of your certificate, then I'd strongly recommend to renew your Apple developer account now.