Brand new battery , checked all fuses, won’t crank won’t start

 

It is cranking but the tachometer doesn't move so either your ESS is disconnected or the starter isn't engaging the flywheel to turn the engine.

 

So what do I do to check those things or what’s my next step lol I’m sorry I’m very new to this I use to have my dad helping me now I don’t it’s just myself trying to do it all alone lol

 

You can hook up an OBD reader to check if any trouble codes are set, first. For the starter, you can just look if the engine belts are turning when you try to start. It does sound like the engine is cranking, but phone audio can be deceiving and it's quick to check. The ESS is under the front main pulley, but you'd get a code if it was not working.

You also risk flooding the engine with the start attempts, so google rx8 deflood procedure. And find a way to charge the battery, start attempts will drain it quickly.

How did this start? What was the last good drive cycle look like? Any other previous issues with the car?

 

[so running the OBD the only code that popped up was U0121 which is data BUS, antilock brake system control module no communication… but also when checking the air filter, it was looked wet and checking my oil. It was really runny like water got into it or something. I don’t know. What could that be do you know?

 

Water in oil looks like a milkshake, light brown, opaque and runny. Mazda prescribes 5w20 oil for RX-8s, and if that's what was used, it's quite thin. Especially if at end of its change interval. Going forward 10w30 or 10w40 are generally preferred.

Was the aie filter wet with oil?

You haven't answered how this started or what the last good drive cycle looked like. There may be clues.

ABS module communication is a weird problem to have, ut wouldn't normally prevent you from starting.

Did you check both the underhood fuse box and the cabin footwell one?

 

So the air filter was wet with what looks to be maybe the oil but idk to be honest and the guys helping me aren’t the best at this lol just my luck..

 

Yes, it's possible to get oil in the air filter from blowby or if the oil is overfilled. It's not a great aign if that's what it is. I would replace the filter and clean the MAF with a MAF cleaner. Wouldn't prevent you from starting but it's another thing to keep an eye on.

Where are you located? There might be a rotary specialist nearby.
I'm not going to be able to help a ton more without answers to the questions asked.