If you are certain that the Poller is up, and the server address is accessible, there may be a special character or space in the nms2.service_managers table.
- Type: mysql nms2
- Type:select * from service_managers;
You can look at the smgr_host and smgr_addr columns and if nothing looks wrong, try running update queries anyway to overwrite the extra character.
Try running these queries to resolve the issue:
update service_managers set smgr_host = 'new system name' where smgr_addr = 'old system name';
update service_managers set smgr_addr = 'new system address' where smgr_addr = 'old system address';