what should the SM and the PO do when the stakeholder unhappy

hi 

I have some question

1-what should the SM and the PO do when the stakeholder unhappy when they sow the Increment in the sprint review ?

2-could the stakeholder see the increment before the sprint review ?

3-Who determines the quality of the product the stakeholder or the scrum team ?and if the stakeholder is not happy when they see the quality what should they do ?

thanks