The WHMCS Auto Install was working fine, but for some reason stopped working recently. I've gone back and reviewed all the setup instructions and everything still looks fine...
We've got the correct encoded version for our PHP, and both Softaculous and WHMCS are using the latest version(s).
I also tried to enable debugging (softaculous_debug.php) both in WHMCS and in a file and neither log anything. There's nothing in the Softaculous error log on the server either. Hard to troubleshoot an encoded script...