[Under investigation] Can't Update Software - Error 004

Let me know if this works for you as I may create a new post to show how I resolved this since my solution replies just get lost or truncated in this new thread format:

A) Clear the Cache which will restart your Roku TV/device
With your remote at the home screen:
1) Press "Home" button 5x
2) Press "Up" button 1x ("^")
3) Press "Rewind" button twice "<<"
4) Press "Fast Forward" button twice ">>"
5) Wait and Roku will restart

B) Manually update Roku (if the Roku TV/device doesn't show the update popup)
1) Go to Settings/System/Software update and either tap okay or scroll right
2) Select "Check Now"
Try to perform the OS update. If it fails then repeat steps A) and B) again

Still fails? 
C) Go to the secret menu:
With your remote at the home screen:
1) press the home button 5x
2) press the fast forward button 3x ">>"
3) press the rewind button 2x "<<"
4) Once in the secret menu, scroll down to "Update software"
5) The Roku will appear to update and then the "Update software" button will gray out
6) Scroll down to "Cancel" -- everything may go blank. Just be patient as the OS should then restart. (This happened to me, but it might not happen to you.)
7) If you see the update screen then proceed. If, instead, you're back at the home screen, then repeat B) and proceed to update that way. If you're still not able to update, then try again because it might work the second time. 

Here is the link to this post, so if this works for you, just copy the link and share it with anyone else who needs to resolve this:
https://community.roku.com/discussions/Known-issues/under-investigation-cant-update-software---error-004/1057216/replies/1078157