Did you run it with an admin? I thought it should save into cacerts file in the user’s profile (AppData), not in Program files. But of course either way works.
I don’t think this process will change before 2.9.0 release, so this solution should work. Here’s the list of issues blocking 2.9.0 for now Issues blocking 2.9.0 release
Although, Smack developer now works on updating Spark to the latest Smack library version and it might have something changed about the certificates, which might require changes to Spark. A minor possibility.