Cucumber tests parallel execution with Testlab

Problem:
I am running Cucumber UI tests with Firebase Testlab. All are working fine. The sequential run is successful and getting all reports.
Currently, I am trying to distribute the tests to run it on Testlab parallelly But seems like it is failing to find the tests.
I am getting some log which says 0 test cases found
```
0 test / 1 shard
1 matrix ids created in 0m 10s
```

It is actually run all the cases sequentially on the 1 shard created. But no parallel runs.
My Gcloud configuration looks like this
```
gcloud:
# test and app are the only required args
app: .apkpath
test: .testapkPath
auto-google-login: false
use-orchestrator: true
instrumentation: true
environment-variables:
coverage: true
coverageFilePath: /sdcard/
clearPackageData: true
directories-to-pull:
- /sdcard/
performance-metrics: false
num-flaky-test-attempts: 0
device:
- model: "NexusLowRes"
version: 29

results-bucket: bucket_name
results-dir: results
locale: en
test-runner-class: CucumberInstrumentationRunner
record-video: true
timeout: 30m
num-uniform-shards: 8 //Not working
```

Cucumber configuration:
```
@CucumberOptions(
features = "features",
glue = "com.test",
tags = {"@mySevenTests"},
monochrome = true)
```

```
class Hooks {
@Rule
var activityTestRule = ActivityTestRule(
InitialActivity::class.java,
shouldLaunchActivity = true,
isInitialTouchMode = true)
.with(MockWebServerExecutorTestTask())

private var activity: Activity? = null

@Before("@mySevenTests")
fun setup(scenario: Scenario) {
activityTestRule.launchActivity(null)
activity = activityTestRule.activity
}

@After("@mySevenTests")
fun tearDown(){
activity?.finish()
}
}
```
**Cucumber Android version `4.8.4`**

Can someone please help on this.