Vauxhall Antara engine stop /start light

Most common cause is a low car battery voltage , worth load checking and also alternator charging rate

Battery cold 12.5v /engine running charging at 14.8v so don't know

This is from owners manual might / might not help . Could try switching on / off

Deactivate the stop-start system
manually by pressing the eco button.
The deactivation is indicated when
the LED in the button extinguishes.

Conditions for an Autostop
The stop-start system checks if each
of the following conditions is fulfilled.
■ The stop-start system is not
manually deactivated
■ the bonnet is fully closed
■ the driver's door is closed or the
driver's seat belt is fastened
■ the vehicle battery is sufficiently
charged and in good condition
■ the engine is warmed up
■ the engine coolant temperature is
not too high or low
■ the engine exhaust temperature is
not too high, e.g. after driving with
high engine load
■ the ambient temperature is not too
low
■ the defrosting function is not
activated
■ the climate control system does not
inhibit an engine stop
■ the brake vacuum is sufficient

Thanks for that i will check all switches and censors are clean and working properly.