Cannot Connect to External identity

I opened a ticket with WatchGuard, but I haven't heard anything from WatchGuard after 24hrs. I'm hoping someone here might be able to help.

I'm trying to setup AuthPoint on my WatchGuard, I'm following the documentation found here: https://www.watchguard.com/help/docs/help-center/en-US/Content/en-US/authpoint/authpoint_deployment-...

I'm currently on Step 4 -- Add an external identity.

My domain for Active Directory is this:

ad.mydomain.com

So for my search base, I put in:

DC=ad,DC=mydomain,DC=com

System Account DN:
CN=username,dc=ad,dc=mydomain,dc=com

I put in the IP address of my AD server for "server Address" and I have LDAPS and server port 636.

I went with the default settings for the rest of the items.

I save it, then go to the 3 dots and hit "Check Connection" and I get: Cannot connect to the external identity.

Obviously, I have something configured wrong, but the error message isn't very helpful. Are there any logs, or anything I can start looking at to try to figure out why it isn't connecting?

I'm almost certain that it's at least trying to connect to my AD server because if I change the IP address it takes a lot longer to connect. I'm positive I have my LDAP search base correct.