Unable to run test in Flow Designer - mulesoft

Question

I am going through MuleSoft's "Development Fundamentals (Mule 4)" and I'm doing one of the walkthroughs - "WT 2-3: Create an integration application with Flow Designer that consumes an API" and on one of the steps (step 23) the test button does not run and consequently, I can't test the REST endpoint, because I don't have a URL to send requests to.
When I click the Test button, it switches to "Refresh" and on the left of the button it says "Project needs to be refreshed".
However, when I click the Refresh button and wait several minutes for the refresh, it goes back to the Test button, which again doesn't work and shows "Project needs to be refreshed" when clicked, so I am stuck in this endless loop.
I tried deleting everything I had done up to that point and started again from scratch, but when I reached that walkthrough again, I had the same problem.
The only things I have in the Flow Designer are an HTTP Listener and "American Flights API". The problem occurs after I add the API. Before I added in the API, I successfully ran the test with an HTTP Listener and a logger.
The HTTP Listener configuration:
path : flights
The "American Flights API" configuration:
host : training4-american-api.cloudhub.io
port : 80
base path : /
protocol : HTTP
The log in the Runtime Manager shows a LifecycleException, but I don't know what is causing it or how to prevent it.
Here is the log from the Runtime Manager:
[2021-08-22 14:56:32.872] INFO com.mulesoft.ch.queue.boot.PersistentQueueCoreExtension [qtp1112210076-38]: The PersistentQueueManager is NOT configured. The normal VM queue manager will be used.
[2021-08-22 14:56:40.483] INFO org.mule.runtime.api.el.AbstractBindingContextBuilderFactory [qtp1112210076-38]: Loaded BindingContextBuilderFactory implementation 'org.mule.runtime.core.api.el.DefaultBindingContextBuilderFactory' from classloader 'org.mule.runtime.module.reboot.internal.MuleContainerSystemClassLoader#740e48c1'
[2021-08-22 14:56:40.874] INFO org.mule.runtime.core.internal.util.journal.TransactionJournal [qtp1112210076-38]: Using files for tx logs /opt/mule/mule-4.3.0/./.mule/americanflightsapp-xslg/queue-tx-log/tx1.log and /opt/mule/mule-4.3.0/./.mule/americanflightsapp-xslg/queue-tx-log/tx2.log
[2021-08-22 14:56:40.882] INFO org.mule.runtime.core.internal.util.journal.TransactionJournal [qtp1112210076-38]: Using files for tx logs /opt/mule/mule-4.3.0/./.mule/americanflightsapp-xslg/queue-xa-tx-log/tx1.log and /opt/mule/mule-4.3.0/./.mule/americanflightsapp-xslg/queue-xa-tx-log/tx2.log
[2021-08-22 14:56:41.137] INFO com.mulesoft.ch.batch.BatchCoreExtension [qtp1112210076-38]: Persistent queues is not enabled for batch module as it was not configured in Cloudhub console
[2021-08-22 14:56:41.168] INFO org.mule.runtime.core.internal.util.queue.QueueXaResourceManager [ArtifactDeployer.start.01]: Starting ResourceManager
[2021-08-22 14:56:41.169] INFO org.mule.runtime.core.internal.util.queue.QueueXaResourceManager [ArtifactDeployer.start.01]: Started ResourceManager
[2021-08-22 14:56:41.207] INFO org.mule.runtime.core.internal.logging.LogUtil [ArtifactDeployer.start.01]:
**********************************************************************
* Application: americanflightsapp-xslg *
* OS encoding: UTF-8, Mule encoding: UTF-8 *
* *
**********************************************************************
[2021-08-22 14:59:47.852] INFO org.mule.runtime.core.internal.util.queue.QueueXaResourceManager [qtp1112210076-39]: Stopping ResourceManager
[2021-08-22 14:59:47.852] INFO org.mule.runtime.core.internal.util.queue.QueueXaResourceManager [qtp1112210076-39]: Stopped ResourceManager
[2021-08-22 14:59:47.867] INFO org.mule.runtime.core.internal.lifecycle.RegistryLifecycleCallback [qtp1112210076-39]: Failure executing phase stop over object DefaultBatchEngine, error is: org.mule.runtime.api.lifecycle.LifecycleException(Failed to invoke lifecycle phase "stop" on object: com.mulesoft.mule.runtime.module.batch.internal.engine.DefaultBatchEngine#2fd96fde)
[2021-08-22 14:59:47.869] INFO org.mule.runtime.module.deployment.impl.internal.artifact.AbstractDeployableArtifact [qtp1112210076-39]: Stopping app 'americanflightsapp-xslg' with no mule context
[2021-08-22 14:59:47.922] INFO org.mule.runtime.core.internal.logging.LogUtil [qtp1112210076-39]:
**********************************************************************
* Application "americanflightsapp-xslg" shut down normally on: *
* 8/22/21 2:59 PM *
* Up for: 0 days, 0 hours, 3 mins, 6.753 sec *
**********************************************************************
Any help is welcome, thank you.

Answer 1

The problem was coming from MuleSoft's side. I reported the problem on their Help Center and got a response that the issue was under investigation. Several days later, the problem was fixed and the Test button on the Flow Designer page is now working correctly.