If it is a cell indicator, n/a means that the counters for this indicator were not retrieved in the PM FILES. It can be caused by a lock/unlock of the cell, or other O&M jobs.
If it is an adjacency indicator, n/a means “0”. For instance
cell 1 – cell 2 : ho inc request = n/a means there was no ho request from cell 1 to cell 2.
cell indicator = n/a is usually quite rare and shouldn’t be a problem. If you really have a lot of it, it means you have a PM campaign problem.