Epic issue not visible on board

Summary

Epic issues were not visible on the project board although all relevant parameters were validated such as epics were associated with the current active sprint and epic panel being enabled.

Cause

There existed an invalid project ID in the board filter query which prevented Epics showing up on project board.

Solution

Navigate to the board -> Configure settings -> General -> Edit filter query and remove the invalid project ID from the JQL of the board filter and save the filter post which epics were visible on the active sprint and board.