We have migrated AEM 6.2 to AEM 6.4. In author, launcher is not getting displayed. In console, we are getting 500 error.
Could you please check if you have launchers at correct place?
Adobe Experience Manager Help | Common Repository Restructuring in AEM 6.4
Do you also see this issue with OOTB launchers or just the custom ones?
A screenshot from launcher console and more details around 500 error would be helpful.
Could be an upgrade bug - please check with customer support to see if you require a hotfix.
You can raise a ticket with AEM support team here . Replicate the issue again and provide har file , aem logs and a screenshot from the browser.
 Generating an HAR file / Troubleshooting your Tender site / Knowledge Base - Tender Support