EMONCMS error feed could not be created undefined

Hi, i have installed emoncms on my raspi, i send the data and i can see the input and create the feeds...

But when i try to create a "wh accumulator" feed from my input i receive the error: feed could not be created undefined and i found a feed in a new no group section... obviously it does not function!

the redis is working... any suggestion?

thanks!