How to troubleshoot an Arduino sensor failure inside a concrete enclosure?

When an Arduino‑based monitoring system placed inside a concrete wall or floor stops transmitting sensor readings, what diagnostic procedure can be followed to determine whether the problem originates from physical damage to the wiring, moisture‑induced corrosion, or a software fault? Outline the steps for visual inspection, continuity testing, isolation of the microcontroller, and firmware verification, and indicate how to roll back changes if a test does not resolve the issue.