3cx phone accounts not saving on iphone 5?

Question

iPhone

the user set up 3cx phone system 14 on iphone 5, send the settings to the user's mail, open the configuration file through the 3cx phone system 14 application is registered .... everything works fine, the calls go. After a while, sometimes 5 minutes, sometimes a day in different ways, the account settings are lost, that is, in the 3cx phone system 14 settings, the account simply disappears and writes no account configuration. Tried to adjust the handles too.
I did all the standard steps.