Problem with iPhone Camera

Hi,
Yesterday, when testing out the Seeing AI app for the first time, I noticed that I wasn't able to take any pictures or capture any text or generally do anything that involved using the camera. At first, I thought it was an issue with Seeing AI as I have an iPhone 5S which, as you know, is one of the older models. I then tried to use the traditional 'camera' app on the iPhone, however when I navigated to the Take Picture button, VoiceOver said 'dimmed'. I have noticed this with both the front and back facing cameras, for example when using Seeing AI, I could not use either camera in the 'person' channel.
I am aware that this is not directly related to accessibility, however it is having an impact on my ability to use apps such as TapTapSee and Seeing AI, apps which I have found benefitial to my ability to live independently. I can still use these apps to recognise photos that are already stored on my iPhone, I just cannot take new ones using the camera. I am a VoiceOver user using an iPhone 5S using the latest software, iOS 11.2.1. I am reluctant to take my phone to an Apple Store because I only got my phone replaced around three weeks ago due to a ddifferent issue. If anybody else has had this problem with their camera and have been able to resolve it independently, any solutions would be greatly appreciated. So far, I have tried restarting my iPhone and that has not resolved the issue and I have also tried waiting for my phone to cool down after using it for long periods of time but that has not solved the problem either.
Thank you in advance,
Alice