I am trying to have IMDB add Whose Line Is It Anyway? to Gary Anthony Williams list of shows. He has been a guest on the show since 2013

Gary Anthony Williams is listed on several episodes of IMDB's Whose Line is it Anyway? (2013).  However Whose Line is it Anyway? is not listed on Gary Anthony Williams' list of shows.  How can it be added to his list of shows.  My attempts to add it has been rejected, it seems, because when I tried to add it, it states that the show is already listed (I.E. it is listed under Whose Line but not under Gary Anthony Williams.)