Your steps are correct as far as importing historical players are concerned, but it's hard to tell what's going wrong with your info, so I can only guess.
Were you in Commish mode??
Did you have the master.csv open in excel when attempting to import? Close it before you try to import.
Was the player you tried to import already existing in the Master.csv or was he one you added??
Check the player to make sure his info is correct..Use the global search on the top left. Type in a players last name, whole name, etc. and hit enter. If ootp can't find that player, then something is wrong in the Master.csv. If ootp finds him, then click his name to bring up his profile screen and click editor. Compare the lahman id with the one you entered when trying to import. Lahman ids are usually the first 5 letters of last name+first 2 letters of first name+number (01,02,03,etc.). Also check the years he played to make sure the year you entered fell within his playing career.
Can't think of anything else at the moment.
