In Salesforce, an "Internal Server Error" or "Data not Available" error message can appear when you click the Edit link next to a page layout in Setup. This error can occur in both Salesforce Classic and Lightning Experience.
This error is typically caused by one of the following:
If the error appears suddenly with no recent changes made to the environment, follow the troubleshooting steps below.
The following steps address the most common causes of this error in both Salesforce Classic and Lightning Experience.
Browser cache and cookie issues can cause web pages to perform abnormally. Clear your browser cache and cookies and retry editing the page layout
Disable the Enhanced Page Layout Editor to test whether the issue is specific to it:
In Salesforce Classic: Go to Setup | Customize | User Interface.
In Lightning Experience: Click the Gear icon, then go to Setup | User Interface | User Interface.
If the error no longer occurs, the Enhanced Page Layout Editor is the source of the issue.
Managed Packages have hidden integrations and dependencies. An expired Managed Package can cause unexpected behavior including this error.
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