Shrimp keep going MIA

[naesco]

You seem to be acclimating them right.
What about water changes?
Are you making sure that your new water is the same salinity and temperature.
What is your salinity? Inverts like salinity at the higher range 1.026
Also look at investing in a new salinity tester because yours may be out of wack and testing higher than it really is.
Lastly when you try again, observe that they are feeding and buy a small one because they may also just be dying of old age.
Good luck