I think you need to check the compression with a gauge. It may have a timing belt problem that threw off the spark timing and/or compression.

The post inside the battery broke somehow. Said he pulled each plug and tested for spark by grounding them and cranking the engine, all were good, also checked compression at that point, checked out good, though I don't think he did an actual compression check with his gauges, air filter is new, well, maybe a month old. Sprayed ether and engine did nothing he said. Electric lock off is working. 5028 hours on unit, we just got the contract so not sure what all has been done to the unit for the from this point back. Any help would be appreciated. Thanks.

When you say broken negative terminal inside battery, do you mean the negative battery terminal connector broke? You need 4 things for an engine to run. Air, fuel, compression and spark. If you have good compression and you have spark at the spark plugs and you have fuel, unit should run. The fact that you have spark tells me your electrical/ignition system is operating. If you spray ether in the carb and you have spark, it should at least try to run momentarily. Do you have a vacuum operated lock off or an electric solenoid type lock off for fuel? How many hours on unit? How do you know plugs are firing? Need more information to properly help you.