Problem with creating button on dashboard

Hello everybody.

First of all sorry for my English, but I am using a translator …

I am writing here because for the moment I have run out of tests to understand where I am wrong and I ask for help …
I installed Emoncms on a hosting service (altervista.org) and configured (I think) everything.
I have an arduino that keeps updating the feeds and here too everything works.
The only thing that doesn’t work (but for me it is vital in this project) is the use of buttons.
I have created a button and already if I go to configure it I do not find the feeds that I have previously created, but I find only “power1, power2, power3 and 1” that I have never created (it doesn’t seem to me at least …).
I tried to select “power1” but when I click it it gives me the error you see in the attached photo …
So I tried to create the feeds power1, power2 and power3, but even so if I set the feed it always gives me the same error.
I have also attached the part of the log that comes out when it gives me an error, but I don’t understand much about it …

For the record, I already have an emoncms 8.4.0 running on another host service. It has been in operation for years and has many buttons all working.
I just wanted to create a more advanced emoncms in order to supplant the old version, but I’m stuck with this problem …

can you help me or make me understand where I’m wrong?

Thank you very much and have a nice day.
Mauro