Troubleshooting a sluggish or 'dead' sourdough starter

Almost certainly not. A sourdough starter is a hardy ecosystem - it survives weeks of neglect, accidental refrigeration, and most beginner mistakes. 'Dead' usually means dormant. The question to answer: is it producing CO2 (bubbles) and smelling tangy after a feed? If yes after 24-48h of effort, it's alive. If absolutely no activity after 3 days of warm, regular feeding, then yes - start a new one.

Feed it warm and let it sit. Discard until ~30g remains, add 30g whole rye + 30g 28°C water. Stir hard - oxygen helps. Place somewhere consistently 24-27°C (oven with light, top of fridge, near a heater). Wait 12 hours. If you see any bubbles or growth, you're back. Feed again, give it 12 more hours. By 24-48h you should have a doubling starter.

Chlorinated tap water suppresses wild yeast. Either filter it or let a jug sit out for 24 hours so the chlorine evaporates. A lid screwed on too tight builds CO2 pressure that can suppress activity (and occasionally pop). The fridge slows the colony to almost nothing - moving from fridge straight to a feed without a counter-acclimation step often looks like death.

Pink, orange, blue, green, or fuzzy mould on the surface or in the jar. Persistent strong solvent / acetone smell that doesn't fade after 2-3 feeds. After a full 5-day rescue protocol, still zero activity. In all three cases, throw it out and start fresh - it's a one-week investment, not a heartbreak.