DIAGNOSIS When all HDMI ports fail simultaneously, it's rarely the ports themselves. It's usually a software glitch that has disabled the HDMI controller chip, or the TV's input source is stuck.
FIX Start with a soft reset. Unplug the TV from power. While it's unplugged, press and hold the physical power button on the TV for 30 seconds. Then, plug it back in and turn it on. Now, try switching inputs using the remote's Source button. If that doesn't work, go to Settings > General & Privacy > System Manager > HDMI Input Signal Plus. Turn this setting OFF for all HDMI ports, restart the TV, then turn it back ON. This resets the handshake protocol.
IF THAT DIDN'T WORK There's a known issue where certain devices (especially older game consoles or cable boxes) can send a signal that "locks" the HDMI board. Disconnect all HDMI cables. Turn on the TV and let it boot to its home screen. Then, with the TV on, reconnect just one known-good device (like a newer Blu-ray player) to HDMI 1. See if it recognizes it.
HEADS UP If you're using an expensive HDMI 2.1 cable, try a basic, certified HDMI 2.0 cable instead. Some ultra-high-speed cables have compatibility issues with the TV's controller and can cause all ports to fail to handshake.