Changing skeletal mesh disables animation / puts character into T

When I bring in the third person blue print, the mannequin is rigged fine. I fix the blueprint issue in the lecture and it still works fine. It animates as I expect. The moment I go in and change its skeletal mesh, the model T poses and does not animate any longer. Even if I go back to the mannequin mesh, the mannequin stays T posed now. What will fix the animation of these characters when you change their mesh? In the video he just changed the mesh and things just worked. Attached image

Using Unity to Animate Game Characters An Introduction to Unity Character Animation

Rigging

Skeletal mesh not appearing in reference pose - Character & Animation - Epic Developer Community Forums

Into the Ocean: Character Animation Essentials in Blender 3D, John Knowles

Unreal Products:Amplify Animation Pack/Manual - Amplify Creations Wiki

Changing skeletal mesh disables animation / puts character into T Pose - Ask - GameDev.tv

Baking out vertex animation in editor with AnimToTexture

Maya Retargeting Workflow: The Ultimate Guide to Retargeting in Autodesk Maya

Character animation — Godot Engine (stable) documentation in English

Finding Nina - Dogstudio

Blender: Character Modeling – Simply Explained

Skinned Mesh Renderer - Unity Manual

How to replace a character without having to retarget all animations? - Character & Animation - Epic Developer Community Forums

How to change the drawOrder in SkeletonAnimation ? - Spine Forum

Body Part Replacement & Mesh/Mask Boundary Troubleshooting