I think I now see your problem - you will want to join by the new field, but it appears there is a space in it --- I don't think that is allowed in using Excel in the join. Correct that in Excel and try the join again, or proceed directly with conversion.
Try conversion to gdb or dbf table, see if it looks okay in ArcMap, then try the join.
Table to Table is in the Conversion toolbox of Data Management...or, if it is already in ArcMap, should be able to simply right-click, export...
EDIT: Check that- I meant 'Table to Table' is in Conversion; 'Copy Rows' is the one in Data Management. Use either if going the Toolbox route...
(if scripting, the suffix aliases):
_conversion
_management