Apple devices still don’t trust the Sectigo Public Server Authentication Root R46. If your site’s SSL cert chains to this root, Safari and other Apple apps may reject the connection or show untrusted certificate errors — even though Windows and most other platforms accept it.
The workaround is to request a reissue of your certificate from your SSL provider, but specifically ask that it be issued under the previous trusted Sectigo root (RSA Domain Validation Secure Server CA → USERTrus RSA) instead of R46.
Until Apple adds R46 to their trust stores, any certs chaining to that root will fail on Apple devices. I’ve been reissuing certs for my sites and Exchange servers so Apple users can connect normally.