Final answer:
Bhai Mani Singh could not pay the amount of Rs.5000 due to the government's financial constraints.
Step-by-step explanation:
Bhai Mani Singh could not pay the amount of Rs.5000 because the national government did not have enough money to fulfill its responsibilities. Requests for money were usually not honored, which resulted in the government's inability to pay for national defense and other obligations.
Based on the given information, it is not clear why Bhai Mani Singh specifically could not pay the amount. However, the overall financial situation of the government played a role in this inability.