As of macOS Sonoma and iOS 17, Safari automatically blocks all third-party cookies by default (via Intelligent Tracking Prevention or ITP). Apple has removed the simple "Always Allow" toggle from the main settings in many recent versions. You cannot fully "enable" third-party cookies in the traditional sense on newer iOS versions; you can only reduce some restrictions. enable third party cookies in safari
If you are trying to enable third-party cookies for a work-related site that absolutely requires them, contact your IT department – they may need to whitelist the domain or use a managed browser policy.