I've produced a couple of sites using iFrame for a Tumblr blog on a 'Latest News page'.
All has been working fine (for years in fact) until my client emailed me this morning to say the page isn't showing the Tumblr posts:
Both of these should show Tumblr, and have been doing for years - but it just seems to have stopped.
Yes. This is one of the consequences of the European GDPR/DSGVO).
If you visit Tumblr from a European based browser, you will be only allowed to see its content, when the visitor has accepted the new Tumblr terms. Just read this: https://www.muse-themes.com/blogs/news/important-news-for-mumblr-users-based-in-the-eu
Even if you update your widget, your site’s visitors won’t get around to accept the new terms in advance.
Not really nice, but an inevitable fact.