Agent unreachable after del/add node to cluster

Dear Expert

i have GC12c to monitor Exadata Machine

i face problem with Grid_home in Node_1
then we follow proceduer for del/add node from RAC

now agent in node_1 unreachable

$emctl status agent

Agent Version : 12.1.0.1.0
OMS Version : (unknown)
Protocol Version : 12.1.0.1.0
Agent Home : /u01/GC_home_last/agent_inst
Agent Binaries : /u01/GC_home_last/core/12.1.0.1.0
Agent Process ID : xxxxx
Parent Process ID : xxxxx
Agent URL : https://xxxxxxxxx
Repository URL : https://xxxxxx
Started at : 2012-02-04 23:36:24
Started by user : oracle
Last Reload : 2012-02-05 09:13:03 ---->emctl upload (manually)
Last successful upload : (none)
Last attempted upload : (none)
Total Megabytes of XML files uploaded so far : 0