I tried "./mach mozregression -n gve" with latest m-c with Pixel 3a aosp. But application did not start . I saw the following log in the terminal, but the application did not start.

0:00.00 INFO: No 'bad' option specified, using 2020-06-08
0:00.00 INFO: No 'good' option specified, using 2009-01-01
0:00.11 INFO: Getting mozilla-central builds between 2009-01-01 and 2020-06-08
0:00.12 INFO: TaskCluster only keeps builds for one year. Using 2019-06-09 14:23:02.148195 instead of 2009-01-01.
0:03.29 INFO: Using c5ddef8c691be9a24a568d349af7b36c81507b9c (pushed on 2019-06-09 09:06:18) for date 2019-06-09 14:23:02.148195
0:03.29 INFO: Using c98948afa16b1fc3f2d4b6af4391b2e475f8416f (pushed on 2020-06-07 21:39:01) for date 2020-06-08
0:06.43 INFO: Testing good and bad builds to ensure that they are really good and bad...
0:06.43 INFO: Downloading build from: https://queue.taskcluster.net/v1/task/AB5ud-bwQKedyHfOum6iEQ/runs/0/artifacts/public%2Fbuild%2Fgeckoview_example.apk
===== Downloaded 100% =====
0:11.50 INFO: Running mozilla-central build built on 2019-06-09 09:47:38.095000, revision c5ddef8c
0:11.52 WARNING: Unable to find application.ini
0:11.52 WARNING: Unable to find platform.ini
0:11.53 INFO: Using adb 1.0.39
0:11.97 INFO: adbd running as root
0:12.08 INFO: su -c setenforce 0 exitcode 0, stdout: None
0:12.40 INFO: /system/bin/ls -1A supported
0:12.50 INFO: Native cp support: True
0:12.61 INFO: Native chmod -R support: True
0:12.72 INFO: Native chown -R support: True
0:12.83 INFO: Ignoring attempt to set SELinux Permissive.
0:12.94 INFO: Native pidof support: True
0:20.65 INFO: Granting important runtime permissions to org.mozilla.geckoview_example
0:21.70 INFO: launch_application: am start -W -n org.mozilla.geckoview_example/org.mozilla.geckoview_example.GeckoViewActivity -a android.intent.action.MAIN --es args "-profile /data/local/tmp/tests/tmpmzwomi_g.mozrunner" --ez use_multiprocess True

Was there any error reported to the device/emulator logcat?

(In reply to Kartikaya Gupta (email:kats@mozilla.com) from comment #1)

Was there any error reported to the device/emulator logcat?

./mach mozregression --debug -n gve may also give some useful information.

This is almost certainly a dupe of bug 1644327 -- let's move any followups there.