I’ve narrowed it down a tiny bit on my end. I rendered a sequence with Movie Render Queue with deferred rendering and Object IDs, and that works as expected.
I rendered a deferred render with Movie Render Graph and Object IDs, and that also worked as expected.
When I switched to Path Tracer in Movie Render Graph, and it did write Object ID layers to the EXR, however they are not recognized in Nuke anymore. Viewing those individual layers in Nuke does show that they contain data, but the cryptomatte node will not recognize them.
I’ve attached two EXRs, one with deferred rendering, one with path tracing.
SEQ_Test_Render_MRG_Deferred.exr (6.6 MB)
SEQ_Test_Render_MRG_PathTraced.exr (8.0 MB)