Cohabitation, mandate for future protection and succession

My partner to whom I was not married died. He had concluded a mandate future protection and appointed our daughter as proxy. This convention has never been implemented. Can my daughter invoke it to settle the estate on her own?

No. The purpose of the mandate for future protection is to allow a designated person (the mandatary) to represent the mandator who could no longer provide for his interests alone (article 477 of the Civil Code). This mandate ends on the death of the principal, whether it has been implemented or not (articles 477 and 2003 of the Civil Code).