How will you approach your boss two days before launch and tell him that you are not ready?

I would apporaach my boss in this way

1. I would highlight/remind the goals of the product and organisation
2. I would clearly explain the problem and most importantly which goal is not being met due to this issue and why 
   1. I would decribe the proper Root Cause Analysis, if RCA is not available, I would mention the amount of time needed to diagnose why this happened
3. I would highlight what the consequences will be if we go ahead with the release, eg: due to incomplete checkout feature, more and more clients will leave platform if they are frustrated with checkout page not allowing them to continue with payment or finish placing order.
4. I would provide a list of solutions to the problem
5. I would then provide a plan on how and when we are going to fix this and also incovle all key folks if alignment is needed in solution process
   1. Provide a plan on how and whom you will collaborate with while delivering the news to clients. Typically with sales and Marketing teams
6. I would the provide a reflection of why this has occured in the first place  and what steps i can take to ensure that this never happens again