“Starting” forever generally means that the attempt to start the process failed.
One thing you could try is using “synchronous” jobs, which don’t require running a background process. This does mean you can’t do as large or long-running of jobs as a background process would allow, though.
Setting this up requires you to make a change in your config/local.config.php file, inside the service_manager and aliases arrays, add a new line (it can go right under the “Omeka\File\Thumbnailer” line that’s there in the default file:
'Omeka\Job\DispatchStrategy' => 'Omeka\Job\DispatchStrategy\Synchronous',