Adrian Gates

delete your prefs

Duplicate callback outputs
In the callback for output(s): layout.children Output 0 (layout.children) is already in use. Any given output can only have one callback that sets it. To resolve this situation, try combining these into one callback function, distinguishing the trigger by using dash.callback_context if necessary.

It's not very intuitive, but simple if you know how. You create a Render Var like you propably already did for the other AOVs. But since the cryptomatte is output directly by the Redshift render engine, it will need to go into a separate file, which you specify in the Render Var node under the Redshift tab, in the Cryptomatte section. You have to set or create the attributes there, and specify an output file. Then it will work fine.