Check the TMS configurations are setup to receive all filetypes.
AEM Sites typically sends XML, JPG, PNG and JSON. If a project contains those items but they are not in the TMS configuration, the job in AEM is submitted correctly, but will error at the Start stage in the workflow.
NOTE: To a normal user in TMS this is not visible; only an Admin user can see. Add the correct filetypes to the configuration, or if testing, try sending only XML from AEM. |