Error in Job Log :
0xe000958b - The selected transport mode is unsupported by the current setup
SGMON Debug :
verbose -[07244] [Originator@6876 sub=IO] Close;
error -[07596] [Originator@6876 sub=Default] [FetchOverHttp] Error in sending request - SSL Exception: error:14077102:SSL routines:SSL23_GET_SERVER_HELLO:unsupported protocol
verbose -[07244] [Originator@6876 sub=IO] shutdown;
error -[07596] [Originator@6876 sub=Default] Cannot use advanced transport modes for Vceneter/moRef=vm-4223/snapshot-48707: .
info -[07596] [Originator@6876 sub=Default] Successfully released all resources.
VixDiskLib_ConnectEx: Advanced transport modes not available for opening moRef=vm-4223. (Cannot use advanced transport modes for VcenterIP/moRef=vm-4223/snapshot-48707: .)
The Backup Job has SAN transport mode selected but it fails to use it.
Backup Exec 20.6 and later versions no more claims full support for this version. Limited or reasonable commercial effort will be provided wherever possible.
Reference article - https://www.veritas.com/content/support/en_US/article.100046727
In this case, the ESXi version was 5.5. build 9919047 ( U3k) and the vCenter was 5.5 build 3721164 (U3d)
After updating vCenter to latest build i.e. 5.5 U3k , SAN transport mode could be used.