Writers trying to embed tweets in their Substack stories are in for a rude surprise: after pasting a link to the site, a message pops up saying that “Twitter has unexpectedly restricted access to embedding tweets in Substack posts” and explaining that the company is working on a fix. The unfortunate situation comes on the heels of Substack announcing Notes, a Twitter competitor.

The issue could cause problems for writers who want to talk about what’s going on with Twitter in their newsletters or about things that are happening on the platform. While screenshots of tweets could work in some cases, they’re less trustworthy because they don’t provide a direct link to the source. Screenshots also won’t help you if you’re trying to, say, embed a video that someone posted on Twitter. (And Twitter seems to be at least somewhat interested in becoming a video platform given that several Blue perks relate to making the video uploading experience better.)

As an example of how useful embedding tweets can be, here’s Substack’s official announcement that it’s looking into the issues:

Substack spokesperson Helen Tobin didn’t comment on whether the issues were caused by changes to Twitter’s API when I asked, instead sharing the same statement tweeted by the company. If they are, though, it would be far from the only platform affected by Twitter’s new API policies, which were announced a week ago.

Since then, various companies have been notifying users that they have to cut out or paywall certain features that interacted with Twitter, and many people who have run bots on the platform have been posting about how they can no longer post like they used to. Here are some of the apps and bots that have been broken:

Buckenham told The Verge that the email was the only communication they’d received from Twitter about the suspension and that they hadn’t expected anything to change until the end of April based on the company’s statement that it’d be depreciating old accounts “over the next 30 days.” “I’ll confess I expected it to be a ratelimit, not the API key being revoked, though,” they said, before adding, “But overall I’m not surprised to find Twitter’s changes rolling out unpredictably.”

Some developers have decried the new API plans as being prohibitively expensive. The “Basic” tier costs $100 a month and lets your app post a maximum of 50,000 tweets per month (with a 3,000 tweet per month limit per user) and read 10,000 tweets per month. There is a free tier, but it only lets you write tweets, not read them. That wouldn’t be useful for, say, the Thread Reader bot that makes strings of posts on the site easier to read.

The API transition has been bumpy, even for those that appear to be in Twitter’s good graces. Earlier this week, WordPress’ API access was suspended, making it so users couldn’t auto-share posts to the platform. The company was eventually able to get it restored and says that it’ll be “working with Twitter directly to ensure this service keeps running without interruption.”

There are several tools that integrate Twitter that do still work. Embeds still work in Ghost, a blogging platform similar to Substack, as well as in The Verge’s content management system (obviously). However, if those tools rely on API access to work, it’s possible there could be problems ahead as Twitter continues to depreciate access to it.