Maybe I can help. 1st off as Mike said make sure the bypass is not tripped from last season. Assuming you made it thru that there are some other things that are common between gas and elastic that will cause the heating to stop. It drove me nuts on my T2499 until I figured it out.
See here. This is out of my 2004 T2499. Your should be the same.
This is the back side of the heater looks like and where the electric element is buried.
First we need to work on the no clicks.
Make sure there is water in the heater. On this panel just turn on the LP gas rocker switch. It will glow red and stay on until you actually shut if off. All that means is the gas system is activated. The little red LED called DSI in the middle is the fault LED but you never made it to the fault stage yet so you will not get a fault. That is a flame fault only. And the electric rocker will stay on all the time too when it is on. It is just a red light to let you know it is truned on. Mike told yoi about the 3 trys and then it will cut out on saftey and that DSI light will come on. But you never made it that far yet.
So with the gas rocker on, red light in the rocker switch should be on, you should hear click click click at the heater. You be outside and have someone inside flip the switch. If no clicks, that is the 1st problem to work thru.
See this pic again
The ECO (Emergency Cut off, a high temp limit switch ) and the T Stat (thermostat) are in series with each other in the safety circuit. If that circuit does not complete itself electric nor gas will work. It will even stop the electric heating from working and gas will never even attempt to start working.
I suspect your connectors have some corrosion on them. Turn the power back off. The red rocker switch and the battery disconnect off and no shore power. Unplug the PC board connectors and look for corrosion. Push the connectors back on and off a few times to reseat it and scrape the connection.
Then the most likely, it the ECO and the Tstat connections. This one be very careful and hold the ECO in the center of the 2 terminals before pulling those connections off. The actual switch is between the 2 wire lugs and is behind the foam cover. And the same for the T stat. Hold that in the center too. That foam is just a cover. Unplug and replug a few times and then try it again.
Mine would drive me nuts with the wire on the T stat. In fact I got to the point that before I ever tried it on electric, I would just flip the gas on, if I heard no clicks, I would shut it off, go out, fiddle with the wire and then wamo, click, click, click would come and I would shut down the gas and turn on the electric as I knew the safety circuit was working. I eventually corrected the corrosion issue and now it works all the time.
See if this helps. Since you had some hot when on electric, your element is most likely OK and the relay to run it is problem OK. No need to crawl in there yet, the problem is outside still at this point as there are no clicks on gas. You may have had it working on electric then it stops and would not restart. On electric you canít hear anything so you never know if it is working or not.
Good luck and hope this helps.
If this does not do it, do you have a volt/ohm meter? We can dig deeper if needed but I think the connections might be your issue.