First off make sure you unplug your unit or turn off breaker before doing anything first. some models the convection fan can take almost up to 10 minutes to start before the fan starts blowing. If you connected the element you replaced properly it sounds like you may have an issue with the main board that is sending the power out. Only way to test that is too pull your elements out one by one and test be very very careful when you test this hot. Pull the connectors off the back of the element and make sure not to have them touch or fall back into back panel, YES EVEN NEUTRAL COLORS CAN BE HOT WHILE YOUR DOING THIS WITH THE CONTROL BOARD OFF EVEN AND IT CAN BE VERY DANGEROUS!. Once you've got the wires through a piece of cardboard or insulator so they don't touch the back of the unit take a voltage reading by turn the oven on and setting it to bake or broil whatever you're testing. Should have at least 120v or more present at the element hook ups. Also check the main board for loose connections for the wires leading down the unit to the elements. If you have no voltage at one of your elements during testing you either have a bad connection/a burned or shorted wire or a main board that is messing up.