Do you see the A.N.A x64.vst in there ? Just to be sure it's not the 32bit version instead.
Are you using the new APFS or the standard MacOS Extended ( Journaled ) volume format on your MacOS SDD or any Case Sensitive APF or MacOS Extended format ??
You can check this using the Disk Utility, selecting your system HDD and right click & select "Get info"
If you are using any Case sensitive option you could try to rename your HDD without any capital letters ( assuming your HDD drive name is SSD capitals right now ) be aware that this could have impact on existing shortcuts or symbolic links that you have on your Mac.
Edit : also it could be worth trying to download a fresh ANA 1.5 .zip archive from S.A web site and make sure it's not related to a corrupted archive file. Those things could happen, I'm finding the free KEKA unzip App very reliable on MacOS. Have you tried to restart your Mac post installation ?
If ANA installation went correctly on your system you should see the following folders on your Mac, aside the vst plugin mentioned before :
SSD/Library/Application Support/Sonic Academy/A.N.A with those folders inside : Data, License ( if not the demo), Presets, Tables, Settings.xml
Another thing it could be related to is a files permission issue under MacOS, you could try to download the free Permission Reset App and try to apply the 3thrd solution from this page http://www.ohanaware.com/support/permissionsreset.php (INFOS) www.ohanaware.com/permissionsreset/PermissionsReset.zip (Download)
Open Permission Reset, just drag & drop the A.N.A x64.vst file from your VST folder onto the top part app and click the "Reset" button, you should be prompted for your Admin password and your are done, then try to reopen Live again, rescan your plugins via Preferences & give it another try.