When you say the the combination of the fields in the two different tables is not showing up, do you mean that only the fields of the original layer that existed before the join are in the table view, or do you mean that you see the field names of the joined table, but all of the records have Null values in those fields? If you see the joined table fields, but all of the records have Null values in those fields, be sure that the format of the actual values that are supposed to be joined are identical on both data sources, including the presence or absence of leading or trailing white space characters, capitalization, dashes/special characters, etc.
If your table is an Excel Spreadsheet you should convert it to a real table with ObjectIDs. ObjectIDs in a data source are required to get the full range of behaviors that are possible when using a join. Creating joins with a data source that has no ObhectIDs, like and Excel Spreadsheet, result in huge limitations on what behaviors are supported.
