Unable to clean Opcache even after having admin tools installed

I switched to php 7 and using nginx fastcgi cache. If I enter ee clean --all , it clears all cache but it says unable to clean opcacche and Redis not install. I have nothing to do with redis but want opcache to be cleaned or cleared. I had already installed complete ee stack by using this command ee stack install --all. Also, I again tried this command ee stack install --admin. But its not cleaning or clearing opcache.

I removed w3tc as I feel nginx fastcgi cache and autoptimize plugin are more than enough for my site.

Please help me fix this issue.