Invalid Session Please Try Restarting Minecraft - when attempting to log in to Realms

When I click the Minecraft Realms button, I am met with this error message: Invalid Session Please Try Restarting Minecraft

What I expected to happen was...:
I expected the issue would be resolved after restarting the game, logging out of the launcher, and rebooting my PC.

What actually happened was...:
The issue persists after doing the above mentioned "solutions".

Steps to Reproduce:
1. Click the "Minecraft Realms" button
2. Receive error message