Volvo 850 How To Easily Fix A Door That Won't Open From The Inside!
This happens when the two rubber bushings around the rod that connects two parts that move together to trip the latch wear out, causing the rod to fall out to the bottom inside of the car door.
There are other videos on TH-cam that show you how to remove the interior of the door in order to access the area to fix. Once you remove the interior door panel and the door speaker, you can proceed with the instructions in this video.
I could not find the short connecting rod that needs to be in place to trip the latch open when you move the interior door opening handle. So, I made one out of electrical wire that I could shape and pass through the two holes where the actual rod would go. It took a little manipulation with needle nose pliers, but was not too difficult. Just make sure that as you connect and shape the wire - that in its relaxed state it is not putting any pull pressure on the side that trips the latch, and that when you pull the interior door opening lever, that it actually works and trips open the latch to open the door. You can test all of this as you do it and before you put the door panel back on. The whole repair should take you less that an hour and require no parts to order. It will save you around $150-250 - which is what a repair shop would typically charge you.