Autodesk Inventor lists assembly-level constraints under component occurences in the browser. However, if you have a problem with an assembly constraint, this can make it difficult to locate the troublesome constraint as you need to expand each component in the browser to see it's associated assembly constraints. As a handy tip, when your in the assembly, use the dropdown arrow indicated in the image to change Inventor into "Modeling view". This will cause all the assembly constraints at that level of the assembly to exist in one folder labelled "Constraints". Now you can quickly scan the folder for any constraints that require your attention. Once done, simply change the dropdown back to "Assembly view". For example, looking at the image I can easily identify "Mate:18" and "Mate:21" as constraints in need of fixing.