I'm still here...still not able to complete the update (now on attempt 27, maybe more). I successfully ported my physical system over to a virtual machine, removed all non-Microsoft tools and drivers that are no longer relevant in its virtual state and still, same failures in that environment. This confirms it's not hardware! My physical system still runs/operates without problems as does the identical virtual system. The only good news is the failure results are much quicker now in the virtual world. Still the same ole boring Update Failed (nothing but a dialog box indicating such), but now it only takes 45 minutes. I've reviewed the setuperr.log (among the many, many others), cleaning it out prior to every attempt, and still get nothing out of the process that provides even a hint of where the problem is or what caused the "failure".
Such a shame this product, as much as it sucks, isn't a vacuum (new business opportunity for Microsoft?).
On to attempt 28!
This may be a stupid question, but do you start the update from "Update & Security">Windows Update? I've done it from there, this one was from there, and I'll do my laptop from there too. I need to correct something I said earlier. I'm not sure what the "dated" update is you're trying to install, but my suggestion for the MCT route is only the May 2020 update. My update was released today to Insiders. Do you know the release date of the update you're trying to install?
I've attempted many scenarios...Windows Update, Update Assistant (both active and via ISO download), Microsoft Catalog, direct ISO download from my VLSC (both 2004.1 and this newer 2004.2). All of them step me through the process accordingly, but none ever complete. When attempting Windows Update, I get an error code and have searched the Internet far and wide for the cause...tried everything from the result of said search and get the same error code, if it completes at all (some attempts spin for days and days and days...64% and 93% are the most common numbers). I've tried various tools to scan the back-end (I.e., Process Monitor/Explorer for one) just to see if I might discover something hung up or stuck - nope. When attempting to complete the update via ISO, it's a bit of a different process, it's essentially conducting an upgrade (blue screen) and the result is, if it ends, the good ole vanilla "Update Failed" dialog box...no error code, no nothing. Much like the update process, this upgrade process can spin for days...I've seen it end in the 50s and 90s (%). Since I virtualized the environment, I've removed all non-essential apps, drivers, etc. I've even attempted to complete the "Keep Nothing" and same result.
It's beyond comical how the system runs tight (ZERO stability issues, NO system crashes and NADA event log entry concerns, etc.) and yet I can't get 2004 to install on a Dell Precision 7520, XEON E3-1505M v6, 32GB DDR4 2400MHz RAM and 512GB NVMe (with tons of space).