Timed out waiting for process to appear on device

You mentioned that restarting Android Studio didn't work for you...but it worked for me...

File > Invalidate Caches / Restart... > Just Restart

Android Studio 3.6.2
Build #AI-192.7142.36.36.6308749, built on March 18, 2020

For me, it took marking the build as "debuggable" in the application build.gradle file.

For example:

android {


    buildTypes {

        // ...

        releaseStaging {
            debuggable true // <- add this line
            signingConfig signingConfigs.release
            applicationIdSuffix ".releaseStaging"
            versionNameSuffix "-STAGING"
            matchingFallbacks = ['release']

Remember to remove this before building release APKs though!!!

There is a bug in the recent Android Studio release. You can revert to previous version or test it from command line.