You want to ask, "Why did the signature raw method fail? What is the solution?" ? The causes and solutions of this problem are as follows:

1. Format error: Please make sure that the signature text is written in an appropriate format. The signature symbol in Markdown format is usually two minus signs at the end of the text.

2. Missing text: confirm whether the signed text exists and has not been accidentally deleted or omitted.

3. Coding problem: If special characters or nonstandard characters are used in the signature, the signature will fail. Try deleting or replacing these characters, or signing in plain text.