Character T-poses after editing character mesh

I am following a tutorial for UE5 after using Blender for a few years, so I know a bit about 3d modelling in general, but Im running into an issue.

When I add a third person character, and click play, everything works well. But if I change the character mesh, and try again, I get the new mesh, but my character T poses everywhere. Every single character that comes with UE5 does this. I have noticed that when I change the mesh, the ‘Animation’ option, ‘Anim Class’ slightly above turns from ThirdPerson_AnimBP_C to None, and ThirdPerson_AnimBP_C isnt in my list of options.

The tutorial I’m following is from the beta of UE5, so I’m wondering if something changed after the full release?

Thanks in advance for any and all help!