A lone { stops at column 2

A single opening brace stops at column 2. The converter shows Expected property name or '}' in JSON at position 1 (line 1 column 2), and the output is cleared. An empty text box is the third of these failures: Unexpected end of JSON input. The characters that were there before the failed parse are gone.

The paste people usually mean is the trailing comma.

{"a":1,}

That one reports Expected double-quoted property name in JSON at position 7 (line 1 column 8). The comma asks for another key. The } is what the parser finds instead. All three of these are parse errors. The page copies that message and leaves the result blank. Parsing stays in the browser.

[] is allowed JSON, so it does not take that path. Laravel prints []. TypeScript drafts this:

export interface Root {

}

The PHP class is still DataTransferObject. It has declare(strict_types=1), no fields, and a constructor with an empty body. CSV rejects the empty array with CSV conversion expects an array of objects.

Take the comma out in the JSON formatter and run the JSON converter again.

The sample object and the other limits are in the guide: https://kepttools.com/guides/json-to-typescript-php-dto-laravel