When the government first shut down, what were lawmakers having trouble reaching an agreement about?

Their argument was on the budget.
The main cause that become a hindrance for a  law to be passed is the budget.
The congress often not agree on which budget allocation they need to prioritize when considering a bill. For example, Congress from Republican party tend to favor to allocate the budget for military while the one from Democratic party tend want to spend it on government programs.

B. it promoted the powers of the executive branch