The application most likely does not have write access to the .winstrom folder.
First, launch the application with debug logging enabled to get more details about the error. You can send this information to technical support for further investigation.
The following error will most likely appear in the debug logs:
ERROR WSAppSettingsHelper:133 - java.io.IOException: Operace zamítnuta
ERROR LoginDialog:290 - cz.winstrom.config.WSAppSettingsHelper$WSAppSettingsException: Nepodařilo se uložit nastavení aplikace.
Linux:
Check the folder permissions using the command ls -Al ~/.winstrom/ — some permissions are likely missing.
Windows:
The folder can be found at: c:\Users\{OS username}\.winstrom\
Right-click the folder and open Properties, where you can review the permissions.