There are features that only work on 2018, but the basic functions such as charge notifications, status, and remote climate control should work. Can you update status or start/stop climate control through the web site using your computer? If the web site works, try uninstalling and reinstalling the Android app. If the web site does not work, you need to talk to Nissan EV Customer Service to resolve the connectivity issue.
Personnaly, I have not updated to the new app. The initial release of the new app had many problems that were noted in other threads on this forum, but Nissan released an update which supposedly fixed those issues. The old app works fine with my BlackBerry PRIV and 2015 SL so I am staying with it.
Edited to add: For charge notifications such as charging stopped or complete to function, email and/or text notifications must be set up through the web site. These notifications use email or text messages and do not depend upon the Android app.
Silver LEAF 2011 SL rear ended (totaled) by in-attentive driver 1/4/2015 at 50,422 miles
Silver LEAF 2015 SL purchased 2/7/2015