Looking at the Indigo forum and release history, Indigo Renderer hasn’t had a meaningful update in several years (2022) It predates macOS Tahoe and SketchUp 2026, so it was never designed with either in mind.
Indigo is also not Apple-silicon native (no M-series build, including M3). It runs via Rosetta, whereas recent versions of SketchUp are Apple-silicon native. That mismatch alone is enough to cause instability, UI issues, or outright failures
Expecting Indigo to work reliably with SU 2026 on modern macOS is unrealistic without an updated, Apple-silicon-native release from the developer.
Time to get a new renderer to match your your new Mac.