Just setup a cluster and added 2 hosts, not sure why it just showed me a red alert showing "Cannot find vSphere HA master agent"
What I did so far is disbaled/enabled HA but still shows up
This usually indicates that the kernel management ports are unable to communicate properly. They might for example have a firewall between them blocking some required ports or packets, or they might be setup on different subnets with no gateway or router to allow them to communicate.
In short the kernel ports need to be configured onto the same network.
Issue has been resolved. I went to the hosts vmkernel port settings and for some reason vsan wasn't checked. Only management is checked. So after I ticked vsan for both hosts vmkernel, it went away and it's now connected.
Thanks for all inputs
Using HA on a VSAN cluster requires a minimum of three Esxi hosts.
There was no indication in your original post that you were using VSAN. It is true that HA uses the VSAN storage network instead of the Management network in such setups.
Anyway the warning stands... 2 hosts is not a supported configuration for HA on a VSAN cluster.
Another thing that may be relevant is that when there are less than four hosts in a VSAN cluster, data cannot be maintained in compliance with the FTT policy, so care must be taken if any host maintenance is required.
Also I don't believe VSAN will auto-recover from a host failure with less than four hosts. Once a failed host is repaired or replaced, the recover process might be manual.