Hi gkretsch.
First up, these 2 devices are in what is called the Connectkey family. Connectkey devices do not have Windows Networking built into them, and what that means for you is, unless they are on a Domain (and registered to it) you cannot scan via hostname. In short, if it isn't on a Domain using DHCP you have to scan via IP.
2nd, Chrome and Xerox do not play well together, and even Firefox is as of late joining in on that. And what this means to you is occasionally, any box you fill in that shows dots (password fields) and the occasional check box, don't actually set when you click apply.
In short, If all else fails, try using IE or Safari, and make sure you scan via IP and not hostname.
3rd, make sure the time is correct, if it is off by 3 or more minutes, and the CWIS page is https, scan will fail to Windows 7 and up, this didn't effect the older devices that did SMB scan via port 139 (SMBv1) but it does for the newer port 445 setup (SMBv2)
(CWIS > Properties > General Setup > Date and time
4th, also in line with some of the above, username formatting is different, it has to be put to the machine exactly as displayed in brackets here. (Again, different than the older SMBv1 ala NetBios over TCP/IP
The Share name has no forwarding or trailing slashes of any kind, literally identical to the shared folder. So if the shared folder on the PC is scAn then that is exactly what you put on the printer setup, not scan, not SCAN, you put scAn.
In short, even if all the settings are right, they can still be wrong. The older machines use very different methods to attain the same thing.
As for firmware, I would update both, but I really can't see the update resolving this issue, it's just an aside.
Here is the update to the 7845.
<If you called in to 2nd level, Canada or USA, please PM me the log number (Don't post it here), You have peaked my interest as while scanning has intricacies , it is 100% doable as long as you understand the changes between the old tech and the new. >