CSRF error on login

Hey guys, new guy here (first post) so I apologize if this is in the wrong place.

I've been building a web app using CI 3, and I've run into a kind of strange problem: on Microsoft Edge, I am getting the CSRF error page ("this action is not allowed" or whatever) whenever I try to login.  I didn't have this problem in development, but the production machine is on a different server.  I just checked my app/config/config.php, and my CSRF settings are exactly the same on both.  They are:

$config['csrf_protection'] = TRUE;
$config['csrf_token_name'] = 'my_token_goes_here';
$config['csrf_cookie_name'] = 'csrf';
$config['csrf_expire'] = 7200;
$config['csrf_regenerate'] = FALSE;
$config['csrf_exclude_uris'] = array();

So this doesn't make a whole lot of sense.  It's definitely not CSRF - I am logging in from the app, not a script - but for some reason CI thinks it is.  Maybe Edge does something wonky with cookies?

Thanks in advance.