XO uses the Needs Attention folder as a last resort. Why do scenerypackages sometimes end up there?
Error with unzipping
One of the things XO checks is if a subfolder inside the actual folder is perhaps the scenerypackage. A zip file often contains an extra parent folder. For the actual package you need to select the folder one level lower:
Error with installation or not a scenerypackage
If XO cannot find any files or folders that are normally present, it will use this folder.
It is possible that this folder is added for other purposes, like scenery development with WED. It can also be documentation. Both are examples that are not valid scenerypackages: XO has no way to place these correctly. But feel free to move them to any folder you want. You could even make a separate subfolder somewhere.
Another possibility is that a package is not installed correctly. A common example is HD Mesh where people forgot to add the Earth nav data folder:
Error files corrupted
This is the most serious error, but happens seldomly: XO encountered an error while reading an APT.dat or DSF file. Perhaps the XoLog can tell you more about why it happened (maybe the file was locked), but if not, it might be advisable to redownload the package. If XO cannot read the file X-Plane cannot too.