If you receive a new invitation to complete an assessment on CodeSignal you have the option to share your existing results OR retake the evaluation and share your new results.
However, if you choose to proceed with a retake and earn a lower score, the company requesting the assessment will only receive your new result, regardless of whether the score is higher or lower than the previous attempt (once validated). However, if a previous result has already been shared with a company, and the same company requests the same assessment from you, the company will still have access to your prior result as well.