Thermostat shows E6 and may indicate 'Wi-Fi module error' or 'Network hardware fault'; cannot connect to app.

Safety note: This issue is low-voltage and generally safe to troubleshoot without shutting off HVAC power, but turn off power if you remove the thermostat from the wall.

Steps:

• Reboot thermostat: Use the on-screen menu to restart the thermostat if available, or remove it from the wall for 30 seconds and reattach.
• Reset network settings: In the Rheem smart thermostat menu, perform a network reset and attempt to reconnect to your Wi-Fi network following Rheem's app instructions.
• Check power stability: Ensure the thermostat is receiving a solid 24VAC between R and C; low voltage can cause Wi-Fi module errors.
• Update firmware: If the thermostat can still connect intermittently, check the Rheem app for available firmware updates and apply them.
• If E6 persists and Wi-Fi remains unavailable: The internal Wi-Fi module is likely defective. Replacement of the thermostat is typically required; contact Rheem support or an authorized dealer.