The reason is that in Ontap Simulator 8.2, the Community Names = public is not added by default. Therefore this is the workaround
1. Login using Credentials, that is Username = admin and password="whatever your password is"
2. Login again by double clicking on the controller name in system manager
3. Go to Cluster, Configuration, System Tools and then SNMP
4. Click Edit and add "public" to the Community Names
SNMP login should work now.