Epic Tag or Label is missing on Sprint board
The board doesn't recognise the Epic Tag or Label for Epics that are not retrieved by the board filter.
Basically, when Epics links created from multiple projects in the Agile board, the Epic tag/label will not appear in the agile board itself unless you add the respective projects in the board filter. This will also have all the epics from the second project displayed in the epics column.
Include Epic in the Board's Filter and then refresh the board page again.
You can change the board filter to something like the following:
project = "Sample Scrum Project" OR (issuetype = Epic AND project = Project2 ) ORDER BY Rank ASC