Using the Polaroid original film it can take up to 15 minutes for a film to develop properly. Once you’ve taken a picture immediately put it somewhere dark as they are still very sensitive to light for a few seconds. Check it after a few minutes. NEVER SHAKE THE PICTURE!!!
If the pictures are blank it could be that the rollers in the camera have become loose so aren’t properly rupturing the chemical tab, this will normally result in a kind of yellowy square where the picture should be.
If it’s all white try using the expose slider on the camera to darken the next image.