Hi,
We have used the same setting for months without any issue, however today we just got a strange error when trying to start the sprint.
The requested board cannot be viewed because it either does not exist or you do not have permission to view it.
I have checked the board and verified that all the permission and filter settings are still correct. I also tried to create a new board but it doesn't help. Please find my screenshot below and much appriciated for any advice.
Thank you 
Sprint start error:

Board Settings:
