I have same issues! My device is a Series 6 running watchOS 8.8.2. I tried to investigate what the exact issue is. I connected my iPhone, which is paired with my Apple Watch, to my MacBook, opened the Console app on macOS, selected the connected iPhone, then went to the watch’s home screen and prepared to tap the built-in app that failed to download. Then I clicked the Start button in Console, tapped the problematic app on the watch, waited for the error message to appear, clicked the Pause button in Console, and searched for error messages related to “install”. Taking Maps as an example, here is the message I got:
`0x16d833000 -[ACXCompanionSyncConnection _onQueue_handleAppInstallFailureMessage:]: Got install failure message from watch for com.apple.NanoMaps (UI=N): Error Domain=IXUserPresentableErrorDomain Code=1 "无法安装“地图”" UserInfo={AlertUser=true, NSLocalizedDescription=无法安装“地图”, NSUnderlyingError=0x14bd26dd0 {Error Domain=ASError Code=20 "Unable to copy asset information from https://mesu.apple.com/systemassets/ for asset type com.apple.MobileAsset.SystemApp" UserInfo={NSDescription=Unable to copy asset information from https://mesu.apple.com/systemassets/ for asset type com.apple.MobileAsset.SystemApp}}, NSLocalizedFailureReason=请稍后再试。}`
It seems that when my phone tried to request information for the Maps app, an error occurred and it couldn’t retrieve information from the CDN at `https://mesu.apple.com/systemassets/`. If you try to ping that CDN or access it directly, both work. I don’t know exactly what causes this. I am using an iPhone 12 mini on iOS 15.6. If any expert familiar with this sees this message, I hope you can help explain it. Thank you!