See mekanism/Mekanism#7500 (comment) for a fuller description but it seems like the class this listener https://github.com/fnuecke/oc2/blob/1.18-forge/src/main/java/li/cil/oc2/common/capabilities/CapabilityRegistry.java#L35 is never registered to the event bus so the listener never gets fired.

Sorry for the delay, finally had some time to catch up with oc2 stuff. Thanks again for letting me know!