Received error BEN-991207 while viewing plan configuration

Summary

You cannot make effective dated updates to the plan function configuration. (BEN-991207)

Content

We are on 18A. All I am trying to do is going thru my benefits plan setup. I am able to click next until I landed on the Eligibility train stop and when I clicked next to go to Enrollment, I got this error. I have visited MOS to get information on this and I am unable to find any information relating to "You cannot make effective dated updates to the plan function configuration. (BEN-991207)".

I was not trying to chang anything just viewing. And it does not matter if I use session effective date 1/1/1951, 1/1/18 (effective date of plan) or current date.