Tranny

First thing I would check would be fluid levels.

Checked it showing just fine what else should I check?

Was torque converter removed or cleaned during tranny rebuild? Was it drained of fluid? I've seen a good tranny rebuild go bad because residual dirty fluid was left in a TC and contaminated the new tranny filter.

Yes new filter new tc I was just going down the road and it hit 3 gears then just down shifted and the lost all gears it’s like nuetral in every gear I put it in.

Try scanning for codes, if you have an electrical issue it may be affecting components of the transmission or clutch, codes like P0756, P0741, P0894, etc., which are shift solenoids, clutch solenoids, and so on, they all require a 5V reference and a problem with that can cause a cascading failure in those circuits. A diagnostic stand can quickly find that sort of problem. I would also reiterate fluid level is critical with a newly rebuilt transmission, its very easy to overfill and have it whip into a froth and lose pressure to the point pump shaft can no longer turn. Fluid levels expand when tranny heats up, which is why it's critical to check fluid level with tranny at proper temperature. If you fill it cold, you'll be way off. Also, new ATF is high in detergents, and can dislodge gunk in the lines and tranny cooler if those were never replaced. That gunk can quickly clog a new filter. If a diagnostic doesn't reveal anything pull the pan and look at the filter. This is all assuming the rebuild and installation were all good.

PS: your answer aren't posting publicly because you used dashes, which can trigger the spam filter. I saw your post in my email alert though.