In System Manager, Right Click on the Device and select List Resources. This will poll the device using the SNMP Community String you have configured. If the Interfaces list correctly, then SNMP is configure Correctly, and you may want to go into Start> Programs> Solarwinds Orion> Advanced Features> Polling Per Second Tuner (forgot the exact name). Make sure that both of the sliders are at or above the recommended number, then restart the NetPerfMon Service. It will take a few minutes for the NetPerfMon Service to start while it grabs the data from SQL to store into RAM, then System Manager will be able to let you back in.
The NTP change on the network device will not effect our Polling, unless you changed the time on the Solarwinds Server or the SQL Server to be in the past. If this happens, Orion will not display data until it polls with the new time stamps and insert that date time into the SQL Database.