A battery that needs charging will cause the flash to cycle slowly.
The fresher the battery, the faster the flash will cycle.
In a room with lots of windows, if the camera and flash are set to Auto, the camera may sense that it does not need to flash at all.
It can also sense that it only needs a little bit of flash.
If you are getting good pictures under that conditon....the camera and flash are working properly.
The flash has a capacitor that has to charge up to a high voltage before it can work. This can take several seconds.
I suggest you use the two step method when using flash.
Frame you shot and press (and hold) the shutter button half way down.
Then reframe the shot and press the shutter button the rest of the way down.
This give the camera time to recharge the flash capacitor and to autofocus.
Then when you do press the button the rest of the way down, the picture will be captured in less than 1/10th of a second.
I used this camera for the first time this weekend. The flash only worked half of the time while in a large room with alot of windows. I was not taking pictures rapidly. I noticed sometimes there would be a 2 to 3 second lag when it would flash.
Is there a problem with the camera? Are there settings I need to change? What are the tips for working with the flash?