Where dId you add grounds? I usually move the ground cable leading from to battery, straight to one of the starter mounting bolts.
Have you replaced the 12v wire from the battery to the start yet?
Also Im wondering if the ignition is not giving a strong enough supply of 12v to activate the starter. You can test this by taking the ignition wire off the solinoid and supplying it power straight from the battery.

If none of these fix or produce a different result then u may want to get the new starter tested, cause that's everything starter related I can think of. The engine isn't seized?

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