Android 4.4.x is to old and is incapable of registering with the servers due to the lack of secure SSL protocols.
We were forced to upgrade the SSL stack on the backend servers to continue to file flight plans ATC, this had the defect of removing several of the older insecure protocols which were the only ones available to Android 4.4,x.
There we some postings about it we'll over a year so (maybe 2 years ago?)