Hi Brian,
Depending the plan you have for your account, there's a maximum of Parallel runs. If your account runs more than its limit, your test will fail to launch. and likely an error / failure should be notified in your repo. i.e.: If your account has a max of 10, when the 11th run/test is launched, it will fail your workflow.
You may be able to set this by looking at the API for
Start Test and set the fields in the test settings (visible in the
result section of the JSON):
"parallelTestsInWorkspace": 1,
"parallelTestsInAccount": 1,
You may se this limit by adding these parameters to your Curl or APII call.
Regards,
Javier