The engine has to be running so it can drive the fluid pump for the transmission. No gears will be engaged with the engine stopped. That is why it appears to be in neutral.
This seems to be an electrical issue so there are two things to look at. First, turn on the head lights and see how bright they are. If they are not on, follow the smaller battery positive wire to the under-hood fuse box and be sure that connection is clean and tight. If the head lights are dim, measure the battery voltage. If it is around 12.2 volts, it is good but discharged. Charge it at a slow rate for an hour, then try to start the engine. If it runs, have the charging system tested. If testing shows a replacement generator is needed, you must replace the battery at the same time to reduce the number of repeat generator failures, unless it is less than about two years old. This has been a big problem for GM vehicle since 1987.
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Monday, August 15th, 2016 AT 9:20 PM