When We use section access this error comes due to data in which we applied section access.
1-If SOUTH is not available in Region field and we use section access then document will not be open and says "failed to open".
2-Firstly check application without section access and use by any user
then use only NTNAME in section access after that use Region(whatever field you are using for section access).
go step by step you will solve your problem.
Which Authorization method, you are using
NTFS authorization (Windows controls file access)
DMS authorization (QlikView controls file access)