As @Krunnie mentioned if you do not rig it then you cannot actually animate your model because your rig is essentially a skeleton for your custom made model. This then allows you to record the animations on a editor; on its timeline.
Check which parts are Anchored. Had lots of trouble with this before. All parts should be unanchored except the HumanoidRootPart if I remember correctly.
You know… maybe try downloading the Legacy Animation Editor plugin? It’s the older version of the Roblox Animation Editor and it works perfectly fine for me. I’ll get you the link in a few seconds.
HRP is not supposed to show in Animation editor (try inserting a blank rig using the rig builder, select, and you’ll see).
The 1st layer joints should all go back to HRP and that’s what the animation is relative to, so it shouldn’t have any keyframes or movement associated with it. It should all be from your Torso and any other connecting parts.
Edit: added a pic to show how a fully set up and correctly anchored rig looks - No HRP in the editor, all joints correctly nested. 1st level (LowerTorso in this case) is implicitly connected to HRP: