If you have an expired certificate error, this is because iOS certificates expire after one year.
To fix this issue, and re-create any expired certificates.
1. Login to https://developer.apple.com/account, click Certificates Identifiers and Profiles
2. Click Identifiers, then click your app ID
3. Scroll down to Push Notifications, and click Configure
4. Under "Production SSL Certificate," create a certificate
5. Upload a certificate signing request (if you don't have one, create it)
6. Download the certificate, and give it a name like "my app push" so you can keep track of it
7. Double click the certificate, this should open up Keychain. Find your certificate, you can search for it if needed.
8. Click the triangle to show your key, then select both the key and the certificate. There should be 2 lines selected. If you don't see a triangle, your key is not attached to your certificate, and it will not work.
Right-click with both lines selected, and choose Export 2 items.
Save the file as my-app-push or whatever you want, and give it a password. We recommend "apppresser" as the password so you don't forget.
This will create the .p12 file you can upload to your push notification settings on myapppresser.com.
To generate a new provisioning profile, click on Profiles under Certificates, Identifiers & Profiles.
Click your expired profile, and click Edit. It should be a distribution, or app store profile that you used to submit the app, not a development profile.
Select a valid distribution certificate, then save. This should be the same certificate used to generate your app store .ipa file. (If you don't have a valid distribution certificate, you need to add one first by clicking on Certificates, then the blue plus button)
Once you have your new certificates, go to your myapppresser.com dashboard and click on your app. Next click push notifications in the left sidebar.