Hi friend.
Perform the following operations to diagnose the problem:
1. When the device version does not match the command
Check whether the NE or U2000 version meets the requirement for using this command or parameter. If the NE or U2000 version does not meet the requirement for using this command or parameter, upgrade the NE or U2000.
Manually synchronize the NE information on the U2000. If the information cannot be synchronized, delete the NE and add it again.
2. When communication with the device fails
Wait until NEs restore to the normal state.
Check the firewall and route configurations and ensure that NEs communicate with the U2000 properly.
Verify that the SNMP protocols configured on NEs and on the U2000 are the same.
Add the U2000 IP address to the access list of the firewall or disable the firewall on NEs.
Delete redundant data that exists on NEs and synchronize NE information again on the U2000.
Thanks.