Turns over but it will not crank

Welcome to 2CarPros.

Have you checked to see if it has fuel and spark to the engine? The easiest way to check is to see if the engine will start for a couple seconds using starting fluid. If it does, then it is fuel related. If it still doesn't even try, it is ignition related.

Now, keep in mind, since you mentioned a loss of power, you could have a plugged catalytic converter. So, once we determine if there is spark and fuel, the converter will need tested.

Here are links to helps with checking those things. The first link walks you through checking a vehicle with a crank no start condition.

https://www.2carpros.com/articles/car-cranks-but-wont-start

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

https://www.2carpros.com/articles/how-to-test-an-ignition-system

Here are a couple links related to catalytic converter symptoms and how to check one. Only do this if you find both spark and fuel are present.

https://www.2carpros.com/articles/bad-catalytic-converter-symptoms

https://www.2carpros.com/articles/how-to-test-a-catalytic-converter

Do these checks and let me know the results.

Take care,
Joe