Not sure this will help anyone, but we ran into this because we had an environment variable with a value that wasn’t quoted. The workflow is set up to run on
workflow_dispatch as well as on
schedule. We also used to have it run on
repository_dispatch before we changed it to
workflow_dispatch. No issues with this until workflow dispatch. Neither the UI nor the API endpoint to trigger a workflow dispatch event worked. Quoting the value fixed it.
env: SOME_ENV_VAR: 2020-01-01
env: SOME_ENV_VAR: "2020-01-01"