So it looks like it was loose wire connectors after all! After successfully replacing the battery, before closing up, I re-seated the wire connectors, then after closing up, I have a fresh new battery and Wi-Fi is back, too! Yesssss! Thank you for all your help, iFixit! More Power!
Could the linear solenoid be the culprit for the flash not popping up? The camera senses low-light but this doesn’t make the flash activate. The manual release button does nothing. Is this solenoid replaceable?
Be careful not to damage the rubber lining around the edge of the front panel. This rubber lining creates a "recess" into which the front glass panel is "seated".