geocaching.com is changing its API to access its data to another technology. That would be a major change to the app. Due to the decreased importance of Windows Phone / Mobile and the resulting reduced user base, the effort for this migration is too high and is therefore not carried out.
The development of the iPhone version of maaloo Geocaching is in heavy development, but will be available later after this date.
The maaloo Geocaching for Windows Phone/Mobile will not be able to communicate with geocaching.com after 1 June 2019.
You can only use the offline functionality of the app. You can import pocket queries (GPX-files) and use them without online connection.
The same happens for the geocaching functionality of maaloo Outdoor.
I hope you enjoyed the app so far and will have it until 1 June 2019 or maybe even beyond as iPhone version later on.