The website took more than 100 seconds. Not you.
Cloudflare connected to the website, then waited 100 seconds for a reply that never came. Reload once. If the page does heavy work, it may fail every time until the owner speeds it up.
Nothing on your side causes this. VPN, cookies and browser do not matter here.
Return a response within 100 seconds: run long jobs in the background and poll, or stream early bytes. Enterprise plans can raise the timeout, but fixing the slow path is the real repair.
Cloudflare’s documentation