Why won't my drone lift off. 3 sides lift, but the right backpropeller

It is most likely the same issue I am having. The pin inside the propeller gear broke. You'll have to replace the pin in the gears

My kids flew my Kaptur Protocol drone into a lavender bush and one propeller stopped working, although it tried to spin, just very slowly.

I took it apart and discovered that the pin holding the main gear had popped, and after pushing down hard on the gear while supporting the bottom of the motor casing, managed to pop it back in. I wish I hadn't had to take apart the entire drone to figure that out, but it works now, thanks to an iFixit contributor!