I'm trying to make a sphere go from size 0.001 to 2.000 over a course of 20 frames. When I scale it in one frame however, it stays that way for all the other frames. I can rotate it, move it, but I cant scale it
When I press i it doesn't do anything except say on the top say "successfully added 3 keyframes for keying set 'LocRot'" but that doesn't help at all.
You need to insert keyframes for changes to values.
Go to frame one, scale the object to 0.001 and with the mouse cursor in the 3d view press I > Scale. Now all frames will have this value. If you change to frame 20 and scale it to 200, you will notice the scale property being orange. Orange means that this value is different than the keyframed one and will be lost after changing frames.
Press I > Scale again to insert another keyframe for this value.
You are likely inserting the wrong kind of keyframe.
Go to frame 1. Press I to insert keyframe. Select anything with Scale in it. LocRotScale, Scale, RotScale.
Go to frame 20. Scale object. Press I to insert keyframe. Again, select something with Scale in it.
Going over your response, you probably involuntarily inserted a keying set. This will automatically set keyframes for predefined parameters, Scale not being part of that Set in your case.
To fix it, you can delete it by opening the keying dropdown on your timeline and pressing the right Key button with the x.
I had the same issue, no answer did fit... until I realized that I experimented a bit with keyframes and I turned them off here:
