If you're unable to enter the stream, your feeder is probably hard at work creating some postcards. You have the option of giving it another go (by clicking the "Check again" button) to see if the event that the picture-taking process has already been completed, or you can choose to wait till they arrive.
In case there are no visitors on the feeder, the sensor was likely triggered by some other movements (rain, falling leaves, moving branches, food moved by the wind...). In this case, try turning your feeder so that it faces another direction with a more fixed background.
If the sensor is triggered by a non-bird object the postcard-taking session will be triggered, however, they will not be pushed into your feed because the recognition process will discard them.