• Open the exact same product or page on desktop and a real phone, using a private browser window. Check whether the feature is absent everywhere or only on one template.
• In the app, review device targeting, display rules, page exclusions and any dismissal or frequency limit. A previously dismissed popup can make testing misleading.
• If the integration uses an app embed or app block, confirm it is enabled in the theme that is actually published. A setting in a draft theme will not update the live store.
• Use the theme editor's mobile preview to look for overlapping sticky bars, cookie banners or elements hidden by responsive styles.
• Test other storefront overlays one at a time in a theme copy. Remember that app-level settings can still affect the live store.

If it still fails, share the app name, theme name/version, affected page path, phone/browser and a screenshot without customer data. Please do not post passwords or access tokens.