Hi!
This is an issue with all Blu phones that have been updated. As of right now, the only workaround is a factory reset. [https://www.google.de/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&cad=rja&uact=8&ved=0ahUKEwi2-d6LtOLXAhVLZVAKHbWYCqYQFggxMAI&url=https%3A%2F%2Fwww.androidcentral.com%2Fhow-factory-reset-android-phone&usg=AOvVaw0dWTZZkbRxicylw9I08Nhk|Here's how to do that], please note that that will wipe all your data.