Some 19.3 updates can cause the stored configuration to be corrupted, returning the processor configuration to Factory Default.
The previous configuration can be restored through recommission. In general, it is recommended to connect to the processor and ensure operation with the client before updating, which will ensure you have the latest configuration before an update. However, the site can be recommissioned from the lastest site configuration for the processor available in the client, or from an AGS backup if necessary. If that isn't available, the site will have to be reconfigured.
This issue is strictly for 19.3 updates and should no longer occur in future releases. If this occurs for any other update, please collect logs and submit a support ticket.