Easy AntiCheat sometimes provides users issues when users know they have installed it correctly. This issue is a common with a few solutions.
Option 1
The first recommended solution for this issue is to try to verify your game to ensure you have not missed files and make sure that the files were all added. Any time you run your launcher, you should do so as administrator because the permissions requirements of many locations that the game needs to write to are restricted by User Access Control (UAC). This solution only occasionally solves this issue though, so often you will want to move to option 2.
Option 2
The second solution for this issue is a little more involved and complicated.
First, open Windows PowerShell as Administrator.
Second, navigate to your installation folder. By default the command will look something like this:
cd "C:\Program Files\Roberts Space Industries\Star Citizen\StarCitizen\LIVE\EasyAntiCheat\"
Then, regardless of which folder you had to navigate to find the easy anticheat eos executable, you will need to run this special command to register Star Citizen with Easy AntiCheat
.\EasyAntiCheat_EOS_Setup.exe install 54540c7a80fe48ea92ead64506b4ff53
This command should register your game with Easy Anticheat and the next time you run your game it shouldn't say Easy Anticheat is not installed.
Caveat
If you are running with any special security such as FIPS, your computer will error out regardless of what other steps you take here. Star Citizen is not compatible with system level cryptographic hardening in any way.