@felipe7263, kindly please be informed that this is a bug that has been recorded in GitHub, which you could follow it here:
KoBoToolbox should solve this issue in its next release. As a temporary fix, I have reset the same for you once again (i.e. the custom report page is now viewable again). This time, if you wish to play around with the custom report, kindly please note the followings:
First, change your browser language to English.
Then you could work with graphs and bars without any issue.
I will let you know when we have a permanent fix for this issue.