Show message on invalid authorization

What message should I show to users when there is a problem with his authentication?

I'm developing an application where there are authentications even when user is already logged (on each request/post to server), so for example, if he changes his e-mail address, password or other critical information, his current login will be invalid.

In this case, if he was using his laptop and made those changes his session on his mobile will be invalid. This is where I want to show this message, to provide feedback that his current session is now invalid and he needs to login again.

But I don't want to show an agressive message because I'm afraid of somethings, for example:

• Make user feels the app is insecure!!!
• Make user feels like he did something wrong and those changes are now invalid.
• Feels like the app isn't integrated with all devices and, somehow, instable/insecure.

My first tought was to display a message like: "Your current session is invalid, please login again".

But I don't know what would be a good pratice on this scenario since it envolves security and users personal information.