Rider is stuck on "Starting ReSharper engine" task when opening a solution

Problem

When opening any solution, the loading doesn't finish. The Background Tasks popup shows that the Starting ReSharper Engine task is running.

Cause

This situation may occur if some security software is present on the machine. Rider uses localhost connection for IPC between its frontend and backend processes, so if anything is blocking network traffic or uses MITM techniques to analyze traffic, the communication between Rider processes may be disrupted.

Resolution

Configure exclusions for the security software to allow connections via localhost.