Hello and welcome to JA.
SSL is a security protocol, and is used to securely encrypt the data transmission.
Normally the SSL capabilities are built-in and ready to use in the application you are using to attempt to login.
If you are getting an SSL error, I would need more info. Is the app causing the error? Or does the app run on the Safari web browser that is Ios dependent.
Additionally, I need to know a little about the Application you are using.....does it have a name? Is it proprietary to your company?
Is the client info backed up? Can you uninstall the app, and then reinstall the app, without losing the client info?
There are many reasons you can get an SSL error. Are you on a public WiFi? Sometimes they block certain ports, that some apps use for their SSL transmissions.