I see out there that lots of folks across multiple devices, mostly ATT customers, have recently been getting a random message (little grey oval) that reads "Can't install app. Not optimized for secure folder" or something very close to that. What's going on and how do we make it stop. I'm on a fully updated S9 with ATT.
I am also having this issue on my AT&T S9. I force stopped and cleared the cache of most apps, rebooted, nothing I've done fixes it. Started after the latest security update, must be a bug in the patch. I'm really surprised to see no comments from Samsung on this yet.
I've been getting this message on my Samsung 9 for several weeks. I didn't notice it corresponding to an update, etc. Depending on what it appears in front of on the screen, I sometimes have to wait for it to disappear to move forward with whatever I'm doing.