Setting up Secondary machine for Webdirec - SSL issue

Primary machine all setup fine with custom wildcard SSL for whole domain - server1.domain.com

Setting up a secondary machine (server2.domain.com) just for Webdirect, follow instructions below to join the secondary machine to the Primary, and getting SSL issues.

Step 6. Configure the secondary machine

• Set up the connection between the secondary and primary machine. Enter the command:

  fmsadmin wpe add [primary] [secondary]

  where [primary] is the primary machine's host name or IP address and [secondary] is the secondary machine's host name or IP address. If you use a host name for a custom SSL certificate installed on either host, you must use a valid, fully qualified host name that is supported by the custom SSL certificate installed on the host machine.

But get the below error, I am using the fully qualified domain name of each server.

FileMaker Server cannot verify the SSL certificate, error: 20632 (SSL certificate verification error)

Both machines are Linux.

I can process with error and say 'yes', which  add the machine to into the Primary a Webdirect machine, but trying to access it via Webdirect results in unable access issues due to SSL I assume not being in place.

Any ideas?