Display is on but unresponsive or frozen; buttons do not work

Safety first: No hydraulic work is needed; keep covers closed unless checking wiring.

• Power cycle: Disconnect power for 5 minutes, then reconnect and observe if the display responds.
• Dry panel: If condensation or moisture is present, gently dry the panel and allow it to air dry fully before re-energizing.
• Test keypad: If some buttons work and others do not, the keypad may be failing. Replace the Viessmann control panel / keypad assembly.
• Board replacement: If the display remains frozen after power cycling and keypad replacement, the control board may need replacement.