The developer has been working on coding and fixing with the new major SLP 4.3. upgrades. Yes, we believe the issue is with WP 4.2.3. “Page iframe not rendering” . There is another WP version is now 4.2.4 update. Not that we expect WP 4.2.4 to fix this, but it is an ongoing battle to keep up with all the changes.
ALL SLP add-on packs are being tested against the SLP 4.3.RC new version release which is nearing publishing for production releases. I will need to check if the Store Pages has a known issue with those upgrades, update your WP to 4.2.4 and see if that fixes anything. You can try out the SLP 4.3.00RC pre-release
But read the latest News and Info and make sure it is on a staging site or test site until it is Published without restrictions, the RC indicates it is stable and has been tested against known variables. There is also a Store Pages “Pre release” alpha version: Same warnings apply, search in products box for other pre-releases of the next version of SLP