This is what the log looks like when the ZRC-90 is communicating correctly; there is one debug line that doesn't change (what I was seeing before), but two others that do change and and info line describing the button push.
dev:592023-07-20 01:44:33.913 PMinfoZRC90a button 7 was pushed
dev:592023-07-20 01:44:33.910 PMdebugCentralSceneNotification: CentralSceneNotification(keyAttributes:0, sceneNumber:7, sequenceNumber:0)
dev:592023-07-20 01:44:33.905 PMdebugparse description: zw device: 11, command: 5B03, payload: 00 00 07 , isMulticast: false
dev:592023-07-20 01:44:17.813 PMdebugparse description: zw device: 11, command: 8003, payload: 64 , isMulticast: false
dev:592023-07-20 01:44:16.298 PMinfoZRC90a button 6 was pushed
dev:592023-07-20 01:44:16.295 PMdebugCentralSceneNotification: CentralSceneNotification(keyAttributes:0, sceneNumber:6, sequenceNumber:255)
dev:592023-07-20 01:44:16.290 PMdebugparse description: zw device: 11, command: 5B03, payload: FF 00 06 , isMulticast: false
dev:592023-07-20 01:43:45.829 PMdebugparse description: zw device: 11, command: 8003, payload: 64 , isMulticast: false
dev:592023-07-20 01:43:44.317 PMinfoZRC90a button 5 was pushed
dev:592023-07-20 01:43:44.311 PMdebugCentralSceneNotification: CentralSceneNotification(keyAttributes:0, sceneNumber:5, sequenceNumber:254)
dev:592023-07-20 01:43:44.306 PMdebugparse description: zw device: 11, command: 5B03, payload: FE 00 05 , isMulticast: false
dev:592023-07-20 01:43:39.484 PMdebugparse description: zw device: 11, command: 8003, payload: 64 , isMulticast: false
dev:592023-07-20 01:43:37.984 PMinfoZRC90a button 4 was pushed
dev:592023-07-20 01:43:37.965 PMdebugCentralSceneNotification: CentralSceneNotification(keyAttributes:0, sceneNumber:4, sequenceNumber:253)
dev:592023-07-20 01:43:37.959 PMdebugparse description: zw device: 11, command: 5B03, payload: FD 00 04 , isMulticast: false
dev:592023-07-20 01:43:27.567 PMdebugparse description: zw device: 11, command: 8003, payload: 64 , isMulticast: false
dev:592023-07-20 01:43:26.046 PMinfoZRC90a button 3 was pushed
dev:592023-07-20 01:43:26.043 PMdebugCentralSceneNotification: CentralSceneNotification(keyAttributes:0, sceneNumber:3, sequenceNumber:252)
dev:592023-07-20 01:43:26.038 PMdebugparse description: zw device: 11, command: 5B03, payload: FC 00 03 , isMulticast: false
dev:592023-07-20 01:43:21.522 PMdebugparse description: zw device: 11, command: 8003, payload: 64 , isMulticast: false
dev:592023-07-20 01:43:20.003 PMinfoZRC90a button 2 was pushed
dev:592023-07-20 01:43:20.000 PMdebugCentralSceneNotification: CentralSceneNotification(keyAttributes:0, sceneNumber:2, sequenceNumber:251)
dev:592023-07-20 01:43:19.995 PMdebugparse description: zw device: 11, command: 5B03, payload: FB 00 02 , isMulticast: false
dev:592023-07-20 01:42:44.103 PMdebugparse description: zw device: 11, command: 8003, payload: 64 , isMulticast: false