Which template are you trying to deploy to Vercel? If you can send me the link to the template/GitHub issue/support ticket, I can try and debug it for you!
Thanks a lot! I just forked books-by-ai, and added a new project in Vercel. The only thing I added was my openai api key, in the enviroment.
Postgres storage must be added to vercel, it will define POSTGRES_PRISMA_URL env variable, which must be added to local .env file, to run locally.
You also need to define OPENAI_API_KEY env variable.