You changed the admin password on all 3 appliances using command 'passwd admin' and the password appears to be changed but you are still unable to login using the new admin credentials.
VMware NSX
VMware NSX-T Datacenter
Incorrect procedure performed for password reset.
In order for the password change to take effect a reset_cluster_credentials file needs to be created as per the documented process.
Resetting the Passwords of an Appliance
Documented process for resetting of passwords needs to be followed as per Resetting the Passwords of an Appliance
KB for a similar issue - Unable to login to NSX UI after resetting admin password from CLI