Transmission will not shift past second gear?

So, my truck won’t go past 2nd gear. I’ve had the truck for about 6 years and used it as a work truck, everything regarding the transmission worked perfectly fine until one day on the expressway when I was driving my car just started to rev up every time I tried to accelerate. That’s the first time my car wouldn’t go past 2nd, assuming it just needed a new transmission I had went to get it rebuilt a few weeks ago and the car was back to driving fine until the same issue happened, I was on the expressway and then it wouldn’t go past 2nd. I took it back to the transmission shop and they say that the issue could be electrical because the cluster doesn't work but the cluster hasn’t been working since, I’ve owned the car so I’m not sure how it was fine for 6 years then now it’s causing the problem. I read online that it could also be a speed sensor, so I swapped them out but still nothing. I brought it to a shop to see if they could figure out the issue, but they couldn’t figure it out either.