UnauthorizedAccessException (Could not find part of the path) when saving a file.C#

I’m trying to save a file with some simple user data in it, following this tutorial.

This is my code:

And this is the error I get:

I don’t understand why this is happening, as when I first compiled the code everything worked and I can’t think of anything I’ve done since then which would have changed it.

I am building for Android.

Your file name contains a colon (“:”). That’s not allowed in Windows.