When typing into a password field on your Apple iOS device it will sometimes switch back to the built-in keyboard and will not allow you to switch to any other keyboard including the EndpointLock keyboard. This is normal behavior.
Within apps on Apple devices text inputs can be marked as a "Secure Text Input" by the app developer. This is typically done on password inputs but it can also be applied to other sensitive inputs like an username or social security number.
When typing into a "Secure Text Input" the Apple device will only allow a special version of its built-in keyboard to be used. When using this keyboard your keystrokes are protected similarly to the way EndpointLock protects you.
However many times these sensitive fields are not marked by the developers and this is aperfect example of how EndpointLock can be used to protect you where Apple does not.
Additionally, when an app launches a web page within the app (a common technique for forgot password functionality) or when visiting any web page from your mobile web browser, any inputs found within these web pages cannot be marked as "Secure Text Input". Leaving EndpointLock as the only way to protect you when typing into a web page.