I also encountered the same problem a few days back in my linuxOS, and when I read about it, I found that this problem is heavily dependent on the system you use and the way you did your setup for angular-cli, both globally and locally.
So, after reading readme.md created by angular-cli for each project, I tried using ng-build --watch but the problem still couldn’t be solved because by running this command it should work like ng-serve but it only build the app and doesn’t even served it on localhost:4200.
then, after digging into the problem more deeper I found the problem, it was with my OS, I am using ubuntu, the inotify/max_user_watches value 8192, which I crossed, due to which it wasn’t showing any changes made further.
So i used these-
echo "fs.inotify.max_user_watches=524288" | sudo tee -a /etc/sysctl.conf
sudo sysctl -p
and it worked fine.
p.s. in the process i also tumbled upon a solution with these commands –
rm -rf nodes_modules/ ->
npm update ->
npm install.
try this before doing above stated canges, if this works for you then you are well and good to go.