Copy-Pasting this cuz it was re-enabled for me a couple of ppl i know.
Tumblr just rolled out a feature that FORCES every account to have safe mode enabled. If you follow artists who do NSFW stuff, the majority of their content will now be autoblocked. Artists, you should make a text only post on your tumblr to let your followers know they need to turn this off to still see your content.
You will need to go into your account settings and turn Safe Mode off. It is now auto enabled on -every- tumblr account