If you ever find that you’re no longer receiving notifications from the iOS app, you can double check on your notification settings by going to Menu > Settings > Notification settings.
If you select Notification settings, you’ll be brought to a page that lists all of your options. Make sure you have your preferences selected here:
If you already have your preferred options selected on this page, sometimes disabling and re-enabling these options helps kick things back into gear. You’ll also want to check and make sure you allow notifications from Patreon in your device’s notification settings. In your phone’s Settings app, if you go to Notifications > Patreon, make sure you have “Allow Notifications” toggled on.