It should sit somewhere near the middle.
Assuming that the sensor is:-
A) - The correct one
and
B) - Of a decent manufacturer
Then the chances are you’re thermostat is either stuck open or maybe not even there (did this temp gauge issue recently occur?)
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Slight aside = I changed my temp gauge sensor earlier this year as my gauge was reading like yours. I had previously fitted a new stat (from Brickwerks) so I knew it wasn't that. The new sensor worked fine and set my needle in the middle. However a few months later and it has started to read low again, not as low as yours, but it only goes about 1/3rd the way up. I checked my vans coolant temp by pointing one of those hand held infra red temperature readout guns at a fat hose in the engine bay when the engine was well up to temperature and it read about 86 degrees, showing that the engine was up to it's correct temperature and it looks like my new sensor has prematurely gone faulty

It was purchased from a very reputable supplier

. I will have to get another at some point, but it can wait now until warmer weather.