Your inventory can't accept more rewards due to its full slots. You must sell items such as clubs and components that you think you don't need anymore. To do that, go to CLUBS > Select low stars or least valuable clubs/components > tap the 'sell' button.
NOTE: Please be cautious about selling items. We highly recommend locking your important clubs and components to avoid selling them accidentally. Tap your important item from your inventory then click the lock icon. See an example below:
