Problem with launching apps with siri

I've been having a problem with siri lately which has persisted since last week.
when I try telling siri to open an app that I have installed, it tells me "you don't seem to have that app" when I know for a fact that I do.
An example of this is me telling siri to launch Facebook and siri telling me you don't seem to have Facebook.
I try speaking really clearly, and when siri speaks back the app I'm trying to get it to launch, the app is being pronounced properly.
Is anyone else having this issue?