I will offer some possible explanations for the issues you describe.
1) I will assume that you developed your connector symbol(s) in a "new" Symbol library. If that's the case, be sure to add the new symbol library to your Style Set (Style Sets / Harness / Design / General Settings / Library Sets).
2) You will not be able to change the number of cavities for a connector if a library part has been assigned to it. Delete the library part number (Edit Connector) and you should be able to adjust the number of cavities. You can hen select another library part number that meets the selected properties.
I hope this helps.
Thank you James. That helps.