You need to plug a default slot into your main out pose of your animation blueprint in order to make the anim montages work.
Step by step guide:
- Create an animation blueprint and assign it to your character
- Navigate to the anim graph of your animation blueprint, right click on an empty space, search for “Default” and get the Default Slot node (it should be a grey node)
- Plug the default slot’s both input and output execution pins. The input (source) one should be connected to an animation / state machine and the output one should be connected to the Out Pose node