I just installed a Presonus Studio 1824 interface and it’s working.
Installed Ivory III and I’m not able to select a MIDI or audio port (they are disabled) from the Cantabile.
Registered and I have MIDI using the internal keyboard.
We’d need more info to troubleshoot… post some pics of the problem areas. Not sure of your exact issue but make sure your ports are enabled. (This is an older version of Cantabile 3 but it’s same idea for 4)
Onscreen keyboard gets midi in port and a midi out.
Your interface also gets a midi in (and a mid out if you want).
Your interface also gets an audio in (if you want to connect an audio input such as a mic, keyboard etc) and an audio out.
If this is an issue with Ivory Cantabile you’re best of contacting Synthogy support - support@synthogy.com because that version of Cantabile is slightly different.
Otherwise post some screen shots so we can see exactly what you’re referring to.