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 SEC has said it’s still helping with fee calculations and “emergency” enforcement matters but has put most rulemaking, filing processing,...