ARC996 will work just fine - you have to understand how to use Dynamic Memory Allocation scanners. Without much more info here, I suspect you have not sat down and allocated systems, sites and groups, along with quick keys, which are vital to these type of scanners to tell them what to scan.
This article addresses that very familiar problem of 'nothing to scan' (anything in blue is a link)
Nothing to Scan - The RadioReference Wiki
No matter what software you use, these new concepts must be understood. I would sit down with the Easier to Read manual for the 996, and keep our DMA FAQ handy - there's a lot of information there that the manual doesn't have.
You can find links for both here...
Programming Your Uniden Scanner - The RadioReference Wiki
best regards..Mike