We have one customer in A/R that we can't get into the Follow up module.  
Click on Follow, password field opens up; we have no passwords on accounts so we just click through.
Warning message pops up: There is no record of AM-L-I of the Rep assigned to this account.  
Click again and get: You are not authorized to view this account.
 
I cannot find AM-L-I anywhere in DBA!!  There is a SM-I-I for Rep passwords, but there was no password set for the rep on this account.
 
After poking around I was able to access Follow up through C/M, but we are still getting the error message on A/R side.
 

Hi Val!  Nice to see your reply  
 
Here's what we discovered - Have to go into System Manager, I - Contact Mgr Maintenance, I- Enter Reps and Passwords.
 
You need to add a rep code here - LOOK FIRST at what you have entered in CM already and use that code.
 
This worked for us, hope it works for you!  Lori

On a followup, the AR person says since this morning (last night we updated), she can no longer access the History link from AR, she has to go to History via Contact Manager.  Would that be the update that changed that, or something else?
 
Val

Yes, as I said I did that already......