NVP vProxy: FLR mount fails "Unable to transfer file vProxy-FLRAgent to VM"

The following error is observed in the vProxy FLR mount session log:

nsrvproxy_flr: vProxy Log: YYYY-MM-DDTHH:mm:SSZ ERROR: [@(#) Build number: NW_BUILD] Unable to install vProxy Agent on 'VM_NAME': Unable to transfer file 'C:\Users\USER_NAME\AppData\Local\Temp\vpvmware0\emc-vProxy-FLRAgent.msi' to VM 'VM_NAME' (VM_MOREF): Put "https://ESXi_HOSTNAME:443/guestFile?id=84&token=TOKEN": read tcp vPROXY_IP_ADDRESS:34888->ESXi_IP_ADDRESS:443: read: connection reset by peer

The vProxy can connect to port 443 on the ESXi host; however, something is closing the connection.

The FLR mount error provides an Application Programming Interface (API) PUT URL. The same "connection reset by peer" error is observed when curl is used on the vProxy to PUT the API URL.

curl -v -X PUT "URL_FROM_VPROXY_MOUNT_LOG"

admin@nsr-vproxy01:~> curl -v -X PUT "https://esx01.amer.lan:443/guestFile?id=84&token=52a27814-105f-0d5e-78f4-0b847878d0ab84"
*   Trying 192.168.9.114:443...
* Connected to esx01.amer.lan (192.168.9.114) port 443 (#0)
* ALPN: offers h2,http/1.1
* Cipher selection: ALL:!EXPORT:!EXPORT40:!EXPORT56:!aNULL:!LOW:!RC4:@STRENGTH
* TLSv1.2 (OUT), TLS handshake, Client hello (1):
* Recv failure: Connection reset by peer
* OpenSSL SSL_connect: Connection reset by peer in connection to esx01.amer.lan:443
* Closing connection 0
curl: (35) Recv failure: Connection reset by peer

This issue is happening outside of NetWorker. Something between the vProxy and ESXi host, or on the ESXi host is not allowing the connection to port 443 to complete.

Consult with the network and VMware administrator regarding the communication between the vProxy and ESXi host on port 443.

All required ports are documented in: NVP vProxy: Troubleshooting Network Connectivity For Backup and Restore Operations

NVP-vProxy: FLR failing - Cannot identify vProxy Agent version on VM