I have the same problem with textures. I double-checked that the content browser is pointing at the right folder on the HDD by using “show in Explorer”. Everything seems to be OK but the textures just don’t show. Probably a mismatch of the versions? Do uasset show up always or are they created for a certain engine version and will only show up if the Engine version matches the uasset version?
[edit] I think I know why: it says you need to install Substance plugin first - which doesn’t work since a couple of months and engine versions 