as you may know, today (25th of May) is GDPR day!
If your site is using the public and free Mobile notifications service (aka Airnotifier) you must contact your site administrator and ask him to update the site registration following this instructions:
Step 1. Log in to your Moodle site and go to Site administration > Registration. Check that the registration information is correct and up to date.Step 2. Click the button "Update registration on Moodle.net". A red popup will be displayed. Follow the link in it and submit your agreement to the new terms.
It is important to do this to avoid any service interruption.
And if you get an error "An error occurred during registration update (Invalid token - token not found)", simply unregister the site, and register it again.