That doesn't work on an L2350.
You have to turn the key backwards from "off" to make the glow system work on an L2350 (and several others).
On cold days even here (cold=under 40 deg F) L2350's needed the spring to glow red. In the dash is a hole with a spring under it. We have to turn the key backwards for about 15 seconds til the spring starts to glow, and then it'll start.
Also-is it possible that the tractor still has summer diesel in it? Winter diesel starts a little easier....
Yes to checking the glow plug operation and compression. You can check compression through the glow plug holes if you have the proper adapter to do so. The harbor junk compression tester is just that. Junk. Mine actually blew up internally and hurt the cheap metal housing. They offered to replace it but I decided that I didn't want another one, I work for a living and depend on my tools to make an accurate diagnosis for our customers, thus if I feed them bad or inaccurate information, there's a chance that we could be doing more work than needed, all on his/her dime-which isn't fair, IMO. I actually bought my gauge "kit" on eBay, wasn't the cheapest but wasn't the most expensive either. The adapters I also got on eBay. I think I've got about $125 tied up in 3 adapters (glow plug adapters) and the gauge/hose assembly. A good name brand kit is about $1500 and comes with more adapters to test through the injector nozzle holes. I use the glow plug holes because on most of the mechanically injected engines the glow plugs are a little easier to get at. The main thing to remember is that you gotta make SURE that the fuel is disabled when doing a compression test, with the injectors still in the holes, any fuel that gets into the cylinder will still burn and cause the engine to start/run while your gauge is screwed into the glow plug hole, and that'll give you a false reading. I did a BX2380 a while back and forgot to disable fuel and it started, gauge was reading 900 psi by time I got it shut back off.
The only time an elevation change would make it harder to start is if the engine's compression was already borderline. On a 2350, I'd like to see 400 psi on a "warm" engine, 380 on a cold engine. Those are what I'd call minimums. If low, check the valve clearance.