issue connecting ADSSP to SDP

Hi there,

As instructed in this page:
https://www.manageengine.com/products/service-desk/help/adminguide/configurations/general/other_me_products.html

I keep getting this error:
Unable to connect ADSelfService Plus server. Please check the server configuration.

We currently have ADSSP running normally and accessible via: https://server.domain.com:0000
(0000 is port number).
This is the set up in SDP:
Server name: server.domain.com
Server port: 0000
Protocol settings: https

I've tried putting in the full address to the server name but still no luck:
https://server.domain.com:0000

Am I missing something here?