Neither the NOL nor capital loss carryforwards are necessarily invalid. Someone (you?) needs to compute the amount used up in those years when it wasn't shown on the returns. The rest, if any, is a valid carryforward.

Don't forget that recent NOLS have to be carried back 5 years unless an election was made to forego the carryback.

Your calculations may suggest that filing amended returns for past years could be beneficial to the client.