Since @Xon has started using a special versioning format to streamline their development, we needed to update our backend to be able to map their released version_string values to the actual version_id values used.
This is a backend change so there is no need for updating the add-on on your site, and you should start getting update notifications for Xon's add-ons correctly again.
Since it was requested by a few customers to allow more add-ons, we decided to add 2 new tiers..
If you currently have e.g. 60 extra add-ons and choose to upgrade to 120 extra, the remaining days on your current license will be prorated, e.g. 50 days remaining on license @ 60 extra add-ons becomes 25 days remainings @ 120 add-ons + 1 year from that date.