Hi MarkCrabtree, the check update option will only update the device if it's using a version of software that was posted on Xerox.com. It sounds like you have three devices that may have been using a version not posted to Xerox.com or the software is old and requires a bridge software prior to the auto firmware update working.
You will need to head over to the support pages and downloand the latest firmware and apply manually. Drivers & Downloads - VersaLink C405 Color Multifunction Printer - Windows 10 x64 - Xerox
Make sure that you know what versio of firware the devices are at prior to downloading and upgrading the firmware. As you can see in the image below, there is a simple to follow flowchart to get you to the correct version. If you apply the incorrect version, you can render the device inoperable.
