WhatsApp Deep Link Fix Needed

I'm seeking an urgent fix for a WhatsApp deep link issue on my website. The current behavior is not aligning with the expected functionality, leading to a poor user experience.

Current Behavior:
- iOS users (especially within in-app browsers like TikTok or Instagram) are being redirected to a download page instead of WhatsApp.
- Android users face intermittent deep link failures, preventing redirection to WhatsApp.

Expected Behavior:
- iOS: Direct redirection to WhatsApp, or to WhatsApp Web if that fails.
- Android: Consistent redirection to WhatsApp via an intent link.

I'm looking for a professional who can:
- Diagnose and fix this deep link issue promptly.
- Implement a solution that varies the deep link behavior based on whether WhatsApp is installed or not.

The ideal freelancer for this project would have:
- Expertise in handling deep links, especially for WhatsApp.
- Experience in troubleshooting issues across different devices and platforms.
- Ability to deliver a swift solution to enhance user experience.