As stated above by Essjay, if the tank is newly set up, and does not have an established biological filter then ammonia from fish food and waste probably killed the shrimp.
If you can check the water quality for ammonia, nitrite, nitrate & pH and post the results here it will give us more information to go on. If you don't have test kits, take a glass full of tank water and another glass of tap water to the local pet shop and ask them to test the water for you. Write the results down and post them here.
If the pet shop says the water is fine, ask for numbers. You should get results like ammonia 0.5, nitrite 0.25, nitrate 25.0, pH 7.2, or something like that.
If the tank is newly set up and does not have an established biological filter, then do not get any more shrimp or fish until the filter has established/ cycled. This will take about 1 month. In the mean time, monitor the ammonia & nitrite levels and do a 75% water change and complete gravel clean if you get any ammonia or nitrite readings. And only feed the fish once every couple of days and do a 75% water change & gravel clean about 4 hours after feeding.
If you don't have a gravel cleaner, get a basic model from the pet shop the next time you go there. A basic model gravel cleaner (like the one in the following link) will let you clean the gunk out of the gravel without removing the gravel from the tank. It will also remove some of the water from the tank.
https://www.about-goldfish.com/aquarium-cleaning.html
Make sure any new water is free of chlorine/ chloramine before it is added to the tank.
Make sure you use "Fish Only" buckets for the fish and never use buckets that have been used for cleaning.