Some third-party apps and websites say that their access was cut off without warning. Twitter previously said that it had plans to shut its API access off in early February, and although it was delayed, the company finally did it, and it has caused a lot of issues with many websites and applications.
The agency is looking more into Twitter practices regarding its security practices with user data. Elon Musk has been raising eyebrows for quite some time, but even more so when he acquired Twitter, and it's not exactly in a flattering light.