Please note that if you changed the setting to write tags *after* you wrote some of those tags, they won't be written. Because the tags write as you change them. So if the option was off, it never got the chance to write those tags.
But never fear, you can tell MC to explicitly write those tags any time you want. (Select some files) > Right click > Library tools > update tags (from library) . This will force MC to write the tags from it's internal library out to the files you have selected, into the file tags.
Brian.