The Pro license is managed by Microsoft server of which we have no control. A glitch to cause this has happened many times for many apps and users. We have been urging Microsoft to fix this permanently. Some users have found the following remedy working for them:
Please note that the app goes back to the free version only if the Microsoft license server tells it specifically that you do not have the license more than 10 times in separate runnings of the app.
If you are interested in knowing more about how we have struggled with this, the following is the saga:
Microsoft In-App-Purchase (IAP) has been having glitches probably from its very start. They have affected all kinds of apps, devices and users. You could take a look at this thread to get some sense about it.
This issue started occurring in March 2015 with our Windows Phone version of IP CENTCOM, we contacted Microsoft about this issue in May 2015 after exhausting all possible ways of addressing it including discussing with fellow developers experiencing the same issue. Microsoft looked into this for about 5 months. They initially suggested creating a new IAP license because the change on their side may affect old licenses. This cannot be a solution because we have to take good care of users who have long supported us by purchasing the Pro licenses. In August 2015, they suggested again creating a new license. For old licenses, they suggested refunding them by handling them individually. In other words, they suggested asking each user to create a case with Microsoft consumer support to request for refund. Based on our experience in dealing with Microsoft support, we do not want to subject everyone of our long time supporters to the process. We decided to give up in seeking any help from Microsoft. We tried every possible way that we can imagine to get around the issue. The frequency of the its occurrence seemed to drop significantly.
The occurrence of this issue started to rise again in May 2016. We decided to give Microsoft support another shot. After some email exchanges, they insisted on requiring a way to reproduce this in order for them to address it. We could not find a way to reproduce it reliably because it was random. The situation had got so much worse in August 2016 that it became highly reproducible for some users, so we asked Microsoft to work directly with those users who graciously agreed to cooperate instead of us relaying messages between Microsoft and them. Unfortunately, Microsoft changed their mind and asked us to request users to deal with Microsoft customer support directly. A user kindly accepted this and chatted with the support for two hours, and in the end, the customer support insisted that it is the developer’s responsibility, so the ball was kicked back to the developer support. However, the developer support told us it is beyond their responsibility and asked us to pay $499 to Microsoft to get help in writing the code dealing with the license. We are confident on the three lines of code copied from Microsoft document for IAP license. At this point of time, we finally gave up on working with Microsoft to address their license service issue, and decided to deal with it by doing whatever we can to get around the glitch.
The development of Windows and Windows Phone apps is effectively subsidized by the revenue from our Android apps. We will do whatever we practically can to sustain this effort. We are grateful to all Pro version users helping us in this endeavor.