If you were common-law with someone during the the first part of 2022, and broke up, then you would be separated, not single. If you have separated or divorced, then you can't be single ever again. You are either separated or divorced until you remarry/partner with someone, at least in the eyes of the CRA.
The way you answered it originally told the program that you were common-law *starting* from March 2022. Switching to single after entering that you were common-law didn't delete your ex-partner's info, hence the error message.
