PrestaShop generally does _attachment not play well with full Cloudflare proxying. In most cases, the most stable setup is to use Cloudflare primarily for DNS management, not for aggressive caching or optimization features.
For CloudFlare and to avoid issues with sessions, cart behavior, geolocation, and dynamic content, only specific records should be proxied (orange cloud) — typically the main domain and www record. Use CF for DNS only.
https://app.screencast.com/hGyYBn9IusbHh