I am having the same issue. I'm afraid this is yet another Adobe "gotcha"moment, which can be added to the long list of Adobe "gotcha" moments I've encountered. In other words, Adobe Document Cloud for Office 365 integration is working just fine, but Adobe has purposely "carved back" the "Fill and Sign" and "Send forSignature" features, which is ridiculous, but not surprising. IMO, like most Adobe quirks, it boiles down to them wanting to nickle and dime their customers. These types of things make it crystal clear to me why Adobe has more/less gone to a subscription based model for most of their product lines becuase subscription based model allows Adobe to have complete control over their products and the tools and features within their products whereas if we as customers had the ability to actually own the software, we could potentially have more freedom and flexibility to implement workarounds to these problems, but no such capabilities under subscription model.
As I've stated many times - Adobe is unfortunately the most complete and feature rich PDF vendor in the marketplace and they know this, which gives them the confidence to bully their customers because there's no other PDF solution out there to keep Adobe honest and make Adobe think that customers might jump ship.
I will say, this "gotcha" takes the cake for me. Usually my frustruation centers around how confusing thier product lines can be to understand from the users perspective. This is just straight up Adobe deciding to literally take away and steal the tools you're paying for because as MikeWWOz has accurately pointed out, it's not as if the subscription doesn't come with "fill and sign" and "send for signature".