the phone is connected to the computer, and the debugging tool opened.
runs cordova run android and the result is packaged successfully, but the page of the phone cannot be displayed. Why?

BUILD SUCCESSFUL in 2s

47 actionable tasks: 1 executed, 46 up-to-date
Built the following apk (s):

    E:\qns-mobile\platforms\android\app\build\outputs\apk\debug\app-debug.apk

ANDROID_HOME=C:Program FilesAndroidandroid-sdk
JAVA_HOME=C:Program FilesjavaJDKjdk
No target specified, deploying to device "KVPBB18209202450".
none
Skipping build.
Built the following apk (s):

    E:\qns-mobile\platforms\android\app\build\outputs\apk\debug\app-debug.apk

Using apk: E:qns-mobileplatformsandroidappbuildoutputsapkdebugapp-debug.apk
Package name: cn.evun.qns
(node:25828) UnhandledPromiseRejectionWarning: Error: C:Program FilesAndroidandroid-sdkplatform-toolsadb.exe: Command failed with exit code 1 Error output:
adb: failed to install adb: failed to install mobile platform and roidappbuildoutputsapkdebugappingdebug. APK: Failure [INSTALL_FAILED_UPDATE_INCOMPATIBLE: Package cn.evun.qns signatures do not match the previously installed version; debugging!]

at ChildProcess.whenDone (E:\qns-mobile\platforms\android\cordova\node_modules\cordova-common\src\superspawn.js:169:23)
at emitTwo (events.js:126:13)
at ChildProcess.emit (events.js:214:7)
at maybeClose (internal/child_process.js:925:16)
at Process.ChildProcess._handle.onexit (internal/child_process.js:209:5)

(node:25828) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch (). (rejection id: 1)
(node:25828) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future,
promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.
PS E:qns-mobile >

what"s wrong with me? I have been troubled for a day
to seek the advice of the great god.