Display MoreMy TX5 Pro has this problem too.
I've managed to solve it by setting the user password in Windows.
In Libreelec go Add Videos -> Browse -> here instead of Windows network (SMB) choose Add network location...
Protocol - Windows network (SMB)
Server name - Your PC ip adress (look for it in network settings in Windows)
Username - your Windows username (not PC name)
Password - password you set in Windows to log in
Now your shares should be visible.
It might work even without setting the password but didn't try it yet.
I believe this might actually be an issue related to a recent windows update that just coincided with an update to LE (or maybe it was present earlier and maybe people didn't notice till doing a fresh install). I've been running the same version of LE for several months and I'm experiencing the same issue (and fix) above. It all happened after my W10 box did the creators update (and various other updates) not only did it reset all my sharing preferences (back to homegroup sharing, etc) but since then I haven't been able to browse shares, manually inputting the IP address works.
Plenty of other posts on the internet regarding the same issue (and specifying IP working) on a range of non MS OS devices.