Bump if anyone is still searching for the answer for this, I’ve figured it out a way to get your renders and exports complete…
I created an animation in AE and exported as an Animation, then converted to Apple ProRes 422 to drop into my 422 ProRes sequence. It kept saying CODEC NOT FOUND, when I tried to render and export.
I ended up converting the original animation to h.264 via MPEG Streamclip, then reconnected the media in FCP. I’m sure there are other formats to convert to, and h.264 can be a bit buggy when editing, but this happened to work for me.
Hope this helps!