Contact
A forecast that looks wrong, a cup missing from the week, a question about the data or the site: all of it is welcome.
By email
Write to contact@fortnitepredcomp.com. Replies usually come within a few days.
On GitHub
If you have a GitHub account, the fastest way to report a problem is to open an issue on the project's repository. Issues are public, so do not include anything personal.
What helps
For a forecast that looks wrong, the most useful details are the cup's name and region, the day it ran, the rank you were looking at, and what the forecast said. For a cup that is missing from the list, the name as Epic lists it in the game and the region.
What cannot be done from here
This is an independent fan project: it cannot change tournament results, scoring, rewards or anyone's account. For those, contact Epic Games through its own support pages.