I imported a .fbx file with its animations, but when I choose an animation, the rig is flipped upside down.
However, when I create an empty animation then the rig isnt flipped upside down
UPDATE:
Thanks to UnderTheBridgeGames I was able to fix this issue. When exporting the model, change the Forward property’s value from -Z to Positive Z and it will work!
Awesome, glad it worked out - thanks for posting, hopefully this will help out anyone else encountering a similar issue
In my case the issue was that in “Import 3D” under “Animation General” I needed to have “Rest Pose Animation” as “Default”, instead of “Default with rotations zeroed out”.
currently facing this issue, none of these solutions are working 
Try manually exporting the animations from blender as .fbx one by one, and make sure to play around with the Forward property before exporting. This has been the solution that I’ve been using lately.
that worked! importing animations through the 3d importer is a little messed up 
I had the same problem, when exported model with animations from Blender and imported them to Roblox Studio. But when loading the animation, the model was flipped upside down while animating.
My solution was to export animations as NLA strips, and untick All Actions.
Nice tutorial I found that explained it to me: " How to Export Animation From Blender For Game Engines Like Unity or Unreal" https://www.youtube.com/watch?v=kUn4jUj4gOk
Hey another fix to this problem.
Most of my rigs use multiple segmented meshes.
For example, here is THE SCARYU.
Each of those individual parts like Leg.l, Leg.r, Lid, Torso all have Motor6ds which hold it together. In theory, these aren’t really needed by default but Roblox wants you to think they are. But it really depends on what you are going to do with this rig.
Now with the 3d importer, Roblox for some reasons decides that the parent root of these Motor6ds should be rotated 180 degrees for the animations.
So to solve this you can either remove this animated joints and replace with Welds. Or you can write a simple script that will go through a keyframe sequence and replace all of those poses related to that parent root Motor6d.
The best of solving/fixing this is by taking note of where the animation grid is located. It should never rotate from the default unanimated pose.
Imported through FBX import in the animation editor.
Imported through the 3d importer aka the flipped messed up animation.
