Initial public offerings and normal policing of the securities industry are on hold as the federal government’s partial shutdown drags into a third week.

Many Securities and Exchange Commission officials can’t respond to emails or calls. Only a few are able to hold meetings. The agency’s normal back-and-forth with companies on capital raising, enforcement matters, and other issues is at a standstill. Ride-sharing companies Uber Technologies Inc. and Lyft Inc. could face delays in launching their highly anticipated IPOs.

The...