Populate subform based on combobox values in the main form

ChanceryItems.Report_Category and SMSReportList.Category are not related, so you can't use that as the Master and Child links for those forms. The datatype of ChanceryItems.REport_Category is Numeric, and the other is Text, so there's little chance of them being properly related at all.

What is your intent with the form? That is, what is the user expected to do with this?

Your table with report types have 2 columns: ID and Name, but in your table is stored name, so you should select name in combobox. Will be enough to change column in combobox parameters:
But will be better to change table SMSReportsList and store there ID.

LSMConsulting:
The purpose is to show Reports based on the category selected from the combo box... in a sub form..