This error often occurs due to Salesforce Clickjack Protection settings, which can block embedded Visualforce pages from loading inside Salesforce Lightning. Since the Apsona Merge Button relies on a Visualforce page, enabling Clickjack protection can cause the “refused to connect” error.
Common Checks (not root cause): My Domain enabled, Clear Apsona cache, Sandbox vs Production URL differences, Profile & Permission settings, and Merge button code placement
Root Cause: Clickjack Protection prevented the Visualforce page from loading.
Resolution: Disable the Clickjack Protection checkbox for the relevant Visualforce pages. Once updated, the Merge Button works normally in Lightning.