Realms Error 401 - Invalid Session ID

Whenever I open the "Minecraft Realms" tab in Minecraft it stays at the standard screen for a second (not showing my realm) and then jumps to a screen saying "Error 401 - Invalid Session ID". I am able to load my Minecraft fine and singleplayer and multiplayer seems to be working fine too. I've tried closing and re-opening the game and deleting my .minecraft folder, but neither works.

(Please note: I am aware that this issue has been posted before, but they have been resolved or closed because there is a duplicate – the trouble is that the duplicate has been resolved because it is a duplicate of the first, meaning that neither of them have actually been fixed, so it would be appreciated if this issue were taken seriously and actually solved. Thanks)