Check you VMKernel portgroup configuration (Management traffic) and also ESXi firewall configuration.
The address is not reachable via network between the hosts.
Try to ping other hosts from one host and repeat it on all hosts.
By default, the Management Network's default gateway address is used as the isolation address. Please check whether this is configured properly and has not accidentally been modified with e.g. configuring vMotion.
Seeing as the other hosts (assuming they are in the same subnet) can ping the isolation address (which is the default gateway for the management VMkernel as Andre points out), we can assume that the default gateway is an ICMP pingable device. Your best bet would be to check the specific host and see if you can ping the default gateway here. You can see what the default gateway is by running the command: esxcli network ip route ipv4 list, which would give you an output like this:
~ # esxcli network ip route ipv4 list
Network Netmask Gateway Interface Source
----------- ------------- ----------- --------- ------
default 0.0.0.0 192.168.1.1 vmk0 MANUAL
192.168.1.0 255.255.255.0 0.0.0.0 vmk0 MANUAL
192.168.2.0 255.255.255.0 0.0.0.0 vmk3 MANUAL
192.168.3.0 255.255.255.0 0.0.0.0 vmk1 MANUAL
The first line is your default gateway. That should be reachable for the hosts in a HA enabled cluster, as they ping this address to check if they have been isolated from the network.
Select the host giving this issue.
Go to Configuration > Networking
Locate the Management VMkernel Port group and click Properties
Select the Management Port Group and Edit > IP settings
Note the default gateway.
Right click the cluster > Edit settings
VMware HA > Advanced Options
Enter the following
das.isolationaddress under option
Enter default gateway IP under value
Right click the host > Reconfigure for HA. @
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Check your default gateway for the host.
Correct the gateway if you changed recently.