are you on a mac computer? or an ipad?
it works on macs, but not on ipads (cus ipads are just glorified phones)
try redownloading
also make sure that your computer allows installing and/or running programs that are not ‘signed’ by apple. it could be that ‘gatekeeper’ is blocking triplea because we don’t have an apple dev license
also, try downloading the .zip version, and read the “mac users read this first.txt” text file. (also, if all else fails, you can run the .zip version by running the mac os script file in it)