Edited Animations won't play, but original unedited will?

Hi, so I’m using the Paragon asset Wraith, in a few experiments to gain a better understanding of animation within Unreal Engine. Using a FPS BP, I have been able to retarget the BP to Wraith. Now, I was able to add 2 input controllers to get 2 of Wraith’s animation montages to play when the keys are pressed. However, I took said animations and edited them, and created new montages. When I replaced the old montages with the new montages, containing the updated animations, they will no longer play?
All I did was edit the position of a few bones within each animation and I have edited the State Machine to include the new montages, but it’s still not working, so I’m confused on where I have gone wrong?
Any help is much appreciated, thank you!