There's a big delay after "Checking SNMP..." line, which means that NetXMS is not getting any reply from the device.
Try running
snmpget -v 2c -c public DEVICE_IP 1.3.6.1.2.1.1.1.0
on NetXMS server - there should be some output. If there's none, please check community string and SNMP protocol versions supported by the device.
