Toyota Repair Problems? Ask a Mechanic for Answers ASAP
Hello and welcome to just answer and allowing me to assist you. I have run into this a few times. The most common thigs I found was things getting into the latch areas , the other is latches seizing and cable problems, You will have to use a light and check for stuff that may be jammed in the latches and try to clean out with a narrow screw driver, then you may have to remove some lower seat covers to access the release cable connection to release it. Hope this gives you some help to resolve your problem and if you require further assistance I'll be happy to do so.
This link may help you out , cheers. https://www.youtube.com/watch?v=nR9zAlR_1T0