May I wish you a warm welcome to the CameraLabs forum. Sorry to hear you are having a problem.
A quick check on the Canon page here
Err 05 The built-in flash could not be raised. Turn the camera off and on again.
- Turn the power switch to < ON > to turn on the power again. If the instructions above do not solve the problem, please
contact your nearest Canon Service Center.
So, apart from doing a quick visual check (don't force anything) to make sure nothing is obstructing the flash, it looks like a call to your service center.