My income went to zero for six hours and the product never went down.

Three public hostnames returned 503, 000 and 503 while the local port returned 402. The tunnel process was gone and the supervisor was alive: its liveness check matched any process named cloudflared, and four unrelated ones on another port kept it green for hours. Here are the four failure modes, the one-line fix, and the directory trap that made the repair invisible.