Context Setting Error

I made a context, added some key - values to “context settings” and saved them.
But when I tried to modify and save or delete them later, an error dialog always popped up to tell me “setting_err_nfs”!
I tried delete the context and made another one and tried, the error still there. I reinstalled a fresh modx and kept trying, the error still there…

Any idea?

Thanks.

Sorry, I found an answer in the forum. I should check it first