Hi, first thing I would do is check to make sure there is still gasoline in the tank and it did not leak out. Next would be to check if it will run on LP still and only has the issue on Gasoline. I would then check the gasoline fuel pressure to verify that the fuel pump is working and supplying the proper amount of fuel pressure to the engine. If all checks out I would try starting it in Gasoline mode with a can of starting fluid to make sure that there is no ignition or electrical issues when switched to Gasoline mode.