iCloud Documents Greyed Out and Not Accessible

Many of my saved documents in iCloud are not able to be uploaded to online sites. They appear greyed out and I'm not able to select them. For example, I downloaded/saved my newest proof of insurance document from my auto insurance provider. If I simply want to look at it, I can select it and open it from my "Documents" folder. However, if I want to upload that same document to another site because I need to submit my proof of insurance, when I attempt to do so that document along with most others I have saved appear to be greyed out and I cannot select them for upload. Why is this happening and how do I fix it?