[Plugin: Tumblr Importer] Absolutely no progress after 24hrs

Clear the credentials and start the process over again. Sometimes that helps.

Note that if your site gets no traffic or you don’t refresh or something, then the importer won’t run and won’t actually do anything.

Also note that your site probably has to be a *.tumblr.com site. If you use your own domain name, try switching the site to not have that while doing the import.