Quick answer: Unity AssetBundle.LoadFromCacheOrDownload (deprecated) failing on HTTPS URLs? Use UnityWebRequestAssetBundle for HTTPS - LoadFromCacheOrDownload doesn't handle TLS.
Migrated server to HTTPS; old loading code fails; UnityWebRequest works.
Use UnityWebRequestAssetBundle
UnityWebRequestAssetBundle.GetAssetBundle(url, hash, crc)HTTPS-aware. Modern API.
Or migrate to Addressables
Addressables uses UnityWebRequest under the hood. Cleaner; HTTPS-ready.
Audit deprecated APIs
Each deprecated call is a candidate. Migrate proactively.
“Deprecated APIs lack new platform support. HTTPS is the visible gap.”
If your project still uses LoadFromCacheOrDownload, the migration is mandatory. The deprecation isn't optional.