Hi Dan
The filter is running fine, it was my fault, daypilot script was being cached by the server so it was running the old build.
Today morning as I started working the DEMO banner appeared on the left side and I noticed what was happening.
With
dp.rows.filter(" ");
dp.init();
is easy to hide all empty rows (in my case out of service hotel rooms) on page loading.
It was usefull to download from the sand box, in other way perhaps I would have never noticed the problem.
I will now donwload the new build from my customer account and replace the script.
Many thanks for your help
Best Regards