First check to see if auto-update has been turned off. That is in the edit preferences, “terms lists” and make sure the boxes are checked.
Then you should open your terms list, ( in EndnoteX-- Tools, Open Terms List, select keywords list) go to the “lists” tab. Before hitting the “Update Lists” you should look at the delimiters selected. I know it will separate them if there are carriage returns, but I don’t know how they imported from Procite. Pick the appropriate delimiters for your library.
Then hit update terms and select the field (which should be defaulted to Keywords) to update your lists.
If it isn’t defaulted/linked to keywords, then you need to change the “Link terms list…” which has the “Linking fields to terms list” information, (Hit ctrl 3 in endnote in windows version.This is also available thru the Endnote Tools menu) and make sure keywords is linked to Keywords terms list --waaaay down the list.