I don't know if this will help anyone, and perhaps my story is a one-off that only happened to me. First of all, I am a huge fan of IK software, I have purchased almost all of it, and I use IK products every time I am in my studio.
Several years ago when I purchased ST 4 Max, it was mailed to me through USPS on a USB drive. ST4 installed and ran perfectly. Over time, IK began to release their software to servers for users to download over the internet, including sound content. At some point, I had a pc crash and had to do a full re-install of ST4. The ability to d/l everything made the install a bit easier, plus I now had complete backups on a data drive.
The mistake I made was assuming that all ST4 MAX sound content was made available for download on IK servers. When I had finished the MAX re-install using downloaded files, ST would occasionally give me an error that a certain sound could not be found. This started me on a quest on this forum and also with support tickets to solve the cause of the missing sounds. The quest is documented on this forum, and the cause of the missing files was never solved.
Until...
many months later, after giving up, I was going through a storage drawer in my studio trying to locate something. I moved the ST4 Max box, and it suddenly occurred to me that the USB drive was in that box. I plugged the drive into my pc, and... you got it... the USB drive had a LOT of sound content on it. I copied the sound content folders to my p.c., and all my missing instrument "errors" disappeared. ALL instruments were present and available. I mentioned all this in a help ticket to Support, but hey, I worked a help desk in my younger days. Things get prioritized, and sometimes things get overlooked. I have no problems and no regrets using IK products! And I hope this might help someone with sound content issues.
