Did you change the thumbnailer? Because, it uses the cli by default.
Anyway, you can import in real time, but the process will be limited to the time of a page load (generally 30 seconds), so only a short set of metadata. If there is no file, it’s not a problem, since the longer in an import is the creation of the thumbnails. Just add this to your config/local.config.php:
'service_manager' => [
'aliases' => [
'Omeka\Job\DispatchStrategy' => 'Omeka\Job\DispatchStrategy\Synchronous',
],
],