as long as you submitted your document and back is processing your loan, but for some reason bank offer letter is not ready within 21 days, you better talk to your agent or with the developer directly to see if they can extend for you since it is not your fault but is the banker fault

make sure you rush the banker or whoever is blocking you from signing the S&P, if the developer is delaying you then just go and argue with them

in other cases where your loan rejected by multiple bank then you better off cancel booking and review your financial status