Hi!
It appears that Tumblr is doing something to break your Tweet embed codes. If I run twttr.widgets.load() in the console I catch an exception about not being able to extract Tweet IDs for the Tweets. Those IDs should be extracted from links to twitter.com in the embed code, but instead, they’ve all been replaced by links to Tumblr’s redirect system, preventing our script from recognizing them as Tweets.
Checking an old Tumblr of my own I see the same problem and no setting to disable it.
We’ll try to investigate and find a solution.
Thanks!
Ben