You should be using an HDMI switch, not a splitter (which you’re trying to use backwards as a combiner). HDMI cables carry computer data, and are only designed to be connected to one device at a time. An HDMI switch box will keep your TV HDMI processing circuitry from being confused.
Otherwise, you’ll need to use another type of connection for one of the two devices.
You should be using an HDMI switch, not a splitter (which you’re trying to use backwards as a combiner). HDMI cables carry computer data, and are only designed to be connected to one device at a time. An HDMI switch box will keep your TV HDMI processing circuitry from being confused.
Otherwise, you’ll need to use another type of connection for one of the two devices.