I have the same problem, but there isn't any solution for me. I can manually download but then I can't install This is the error: Downloading iOS 18.4 Simulator (22E238): Preparing to download...2025-04-11 10:47:56.650 xcodebuild[25491:843369] DVTDownloadable: Download Failed. Downloadable: { authentication = none; category = simulator; contentType = cryptexDiskImage; dictionaryVersion = 2; downloadMethod = mobileAsset; fileSize = 8858434688; identifier = "com.apple.dmg.iPhoneSimulatorSDK18_4"; isInternalContent = 0; isUserInitiated = 1; name = "iOS 18.4 Simulator (22E238)"; platform = "com.apple.platform.iphoneos"; simulatorVersion = { buildUpdate = 22E238; version = "18.4"; }; version = "18.4.0.0"; }. Download failed. Downloading iOS 18.4 Simulator (22E238): Error: Error Domain=DVTDownloadableErrorDomain Code=41 "Download failed." UserInfo={NSLocalizedDescription=Download failed., NSUnderlyingError=0x60000332b020 {Error Domain=DVTDownloadsUtilitiesErrorDomain Code=-1 "Failed fetching catalog for assetType (com.apple.MobileAsset.iOSSimulatorRuntime), serverParameters ({ RequestedBuild = 22E238; })" UserInfo={NSLocalizedDescription=Failed fetching catalog for assetType (com.apple.MobileAsset.iOSSimulatorRuntime), serverParameters ({ RequestedBuild = 22E238; }), NSUnderlyingError=0x600001fc5740 {Error Domain=com.apple.MobileAssetError.Download Code=13 "Download is not allowed as mobileassetd was starting up. (Catalog download for com.apple.MobileAsset.iOSSimulatorRuntime)" UserInfo={NSLocalizedDescription=Download is not allowed as mobileassetd was starting up. (Catalog download for com.apple.MobileAsset.iOSSimulatorRuntime), retryWithBackoff=true}}}}}

It is the same for me!

I have the same issue on a iMac with intel processor I can't download the ios 18.4 This is the error message: Download failed. Domain: DVTDownloadableErrorDomain Code: 41 User Info: { DVTErrorCreationDateKey = "2025-04-09 16:12:11 +0000"; } Download failed. Domain: DVTDownloadableErrorDomain Code: 41 Failed fetching catalog for assetType (com.apple.MobileAsset.iOSSimulatorRuntime), serverParameters ({ RequestedBuild = 22E238; }) Domain: DVTDownloadsUtilitiesErrorDomain Code: -1 Download is not allowed as mobileassetd was starting up. (Catalog download for com.apple.MobileAsset.iOSSimulatorRuntime) Domain: com.apple.MobileAssetError.Download Code: 13 User Info: { retryWithBackoff = 1; } System Information macOS Version 15.4 (Build 24E248) Xcode 16.3 (23785) (Build 16E140) Timestamp: 2025-04-09T18:12:11+02:00