The WAF can’t be disabled as a whole, you’ll need to go in and disable specific rules or features as needed, or change the DNS record to “DNS only” so requests don’t pass through Cloudflare at all.
If you are trying to allow something that is blocked or challenged, check your security event log for the specific reason the request was blocked and then adjust your Cloudflare rules and features specifically and as narrowly as you can. https://dash.cloudflare.com/?to=/:account/:zone/security/events