RepricerExpress has been designed to update your standard Amazon price. If you are running a temporary sale on Amazon (set a date for the sale to start, end and a Sale Price), then RepricerExpress wouldn't be able to price this for you as Amazons API doesn't retrieve it.
If you are having a temporary sale there are a few things you can do:
- Stop using a Sale Price. You can use RepricerExpress to drop your price in a 'Sale', you don't need to use this feature on Amazon.
- Set this product to 'Not reprice'. More info here.