If your chocolate is seizing up or not melting properly then it could be a couple different problems.  Old chocolate will not want to melt but you can add a tablespoon of shortening or paramount crystals to help with the melting process.  Seized chocolate can also happen if you get it to hot and don’t stir it properly.  Chocolate will burn quickly!!  Remember to stir often, especially in the beginning stages of melting chocolate.  Low temperature and when microwaving, do no more than 30 second intervals and stir in-between intervals. If water encounters your chocolate, it will seize and can not be recovered.  So, keep the water away from your chocolate.