Steve,
Press the Option key and move your cursor over the black Apple on your menu bar. That should change the first item from "About This Mac" to "System Information...". When the System Info window comes up, look for "Software" in the left-hand list. In that section, scroll as needed to find "Extensions" and click that label. You will now see an alphabetized list of extensions, at least one of which will be your SilabUSBDriver. If there is one or more, look at the "Loaded" column for the one that says "Yes". It should also have "Yes" in the "Notarized" column and "Identified Developer" in the "Obtained from" column.
I don't think mine is the newest and I'm still running Mojave macOS 10.14, anyway. But here is my info on my Silab driver:Version: 408.250.3
Last Modified: 8/22/18, 10:37 PM
Bundle ID: com.apple.iokit.SCSITaskUserClient
Notarized: Yes
Loaded: No
Get Info String:408.250.3, Copyright © 1999-2016 Apple Inc. All rights reserved.
Obtained from: Apple
Kind: Intel
Architectures: x86_64
64-Bit (Intel): Yes
Location: /System/Library/Extensions/IOSCSIArchitectureModelFamily.kext/
Contents/PlugIns/SCSITaskUserClient.kext
Kext Version: 408.250.3
Loadable: Yes
Dependencies: Satisfied
Signed by: Software Signing, Apple Code Signing Certification Authority, Apple Root CA
Since yours is still working, it's gotta be 64 bits. It may be that it is an older one not correctly or currently signed?