So some may have a problem where the keyframes do not show when animating with he default Roblox animator. You are able to move the body parts but doesn’t show a keyframe.
Something like this:
Heres how you fix it!
Step 1: Select your model and scroll down to Primary Part
Step 2: Change the Primary Part to HumanoidRootPart
This should fix the issue. You may need to do this for every model since roblox is defaulting the head as the primary part of a character. Either way, I hope this helped you out.
Have a good day!