What is the device model that you have? Have you tried the external keyboard on a friend's device? Also consider clearing your system's entire cache using the app called App Cache cleaner available on Google Play. Well, if you just bought the set (or got the external keyboard separately), then it may still be under its manufacturer's warranty which would qualify you for a free replacement/service if you go via your retailer (the shop you purchased the product from). Comment below should need be.