Measuring resistance through the heating element while submursed in water is not a reliable test because water is a conductor. To test it, you can ensure proper voltage is present and check with an amp meter for current draw or pull the element and test the resistance. You should be OK though since its new.
I only worked on a couple hot tubs but like previously mentioned there is a switch to ensure theres water flow which must be satisfied before the element will get energized. I'm not sure if it's a pressure switch or flow switch but reading the schematic should tell you.