Hi,
sorry for late reply, it's a weekend for us.
fixed on your site!
this error seems to come only on your site, anyway I found a workaround! we will add this in next release (end on next week).
Changes:
in file /administrator/components/com_jsn/models/users.php and /administrator/components/com_jsn/models/user.php at line 12 I have replaced this
include
with this
require_once