If your Smart Vent's LED is flashing red, it's likely not getting enough power to operate its louvers. There could be a few causes for this: the batteries aren't making full contact with the power, there is an obstruction of some kind, or the louvres have become unaligned. A good place to start is this video:
Next, you can try removing the vent from its duct and setting it on a flat surface. Then eject the battery cartridge, close the louvres fully with the manual lever on the front, and then insert the cartridge again.
If it's still displaying a red LED and having trouble operating freely, please contact support for further assistance.