If you are sure that your batteries are in good shape and have 12 volts plus I would then say its time to replace the solenoid.
The solenoid when energized with 12 volts pulled a metal shaft down against a small spring and it connects the two large terminals.
Over time the oil can become weaker as well as the contact could be burnt.
It is a few years old.
Found one on Ebay $31.75 , Free Shipping and No Tax.
https://www.ebay.com/itm/Intellitec-...from=R40&rt=nc
$68 for you in Canada