Hello,
Welcome to Microsoft Q&A!
As the error info said, the project miss Certificate file, for solving this problem, you could click Package.appxmanifest file -> Packing - >Chose certificate -> Create to make your own test certificate, and then you will build the project successfully.
Thank you.
If the answer is the right solution, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.