https://twitter.com/TammyTexoma/status/1332598326383013888

Someone is impersonating Sidney Powell on twitter, and Twitter is helping them by preventing you from identifying who they are impersonating when you report them.

Even if you copy/paste @SidneyPowell1 in their form, it doesn't find it, so your only option is to select some different user in their list. When you try to submit with it pasted, it clears the form and fails to submit.