There is a problem with the hinge chain.

leewho1

http://ko.esotericsoftware.com/blog/2D-and-3D-physics-for-spine-unity

I followed the construction of the hinge chain, but it does not flip with an error like the capture screen. Looking at the error, 'skeletonRenderer' is null. Unity Runtime versions 3.7, 3.8, and 3.9 all have the same symptoms. What should I do?

Harald

We are sorry for the inconvenience! Thanks very much for reporting this problem.
It has just been fixed, you can download the upated unitypackages here as usual:
Spine Unity Download

Newly created 2D Hinge Chains will no longer have this issue. In case you have saved your scene in the problematic spine-unity version 2020-03-11 that lost the SkeletonRenderer reference, please manually re-assign the SkeletonRenderer reference at the ActivateBasedOnFlipDirection Component. The Component can be found at the hinge chain root GameObject (named <skeletonname> HingeChain Parent <root bone name>).

The issue has been tracked under this ticket id:
https://github.com/EsotericSoftware/spine-runtimes/issues/1643

Thanks again for reporting!