NVP-vProxy: FLR Mount Fails with i/o timeout error when using domain accounts

NVP vProxy FLR mount operation fails when using a domain user account.
The C:\Program Files (x86)\EMC\vProxy FLR Agent\logs\vflragentd\vflragentd-agent.log on the target Virtual Machine (VM) shows

2026-02-18T10:03:39+01:00 INFO:   VPROXY_IP:54588: Remote authenticity verified.
2026-02-18T10:05:45+01:00 INFO:   VPROXY_IP:54588: Authenticated user 'username@domain'.
2026-02-18T10:05:45+01:00 ERROR:  VPROXY_IP:54588: Unable to send message MsgAuthReply '59': write tcp VM_IP:9613->VPROXY_IP:54588: i/o timeout
2026-02-18T10:05:45+01:00 ERROR:  VPROXY_IP:54588: Unable to receive message: write tcp VM_IP:9613->VPROXY_IP:54588: i/o timeout
2026-02-18T10:05:45+01:00 ERROR:  VPROXY_IP:54588: Unable to send message MsgToken '60': write tcp VM_IP:9613->VPROXY_IP:54588: i/o timeout

FLR mount succeeds when using a VM local OS account. It may intermittently succeed when using a domain account.

This issue is occurring due to delayed authentication between the target VM and the domain server. The vProxy uses a hard coded authentication timeout (2 minutes). The domain authentication may complete successfully; however, if it exceeds the authentication timeout, the FLR mount times out and drops the MsgAuthReply sent from the VM's vfragentd. In the example shown in the symptoms field, the authentication took two minutes and six seconds; thereby exceeding the authentication timeout.

The vProxy is working as designed. The timeout was introduced in vProxy 4.3.x as a part of security hardening measures.  
This issue is occurring outside of NetWorker. Delayed domain authentication must be investigated by network and domain administrators. Identify the cause of delays and resolve the issue within the environment.

Workaround:

Use a local OS account on the target VM to mount the FLR.