When you go to Create Menus, and click on the various drop-downs, do you see a full compliment of Menu Sets?
Yes I see some disc menus available over there.Also I have checked under themes and I see a no. of themes available in the software
I do not recall the exact number of such Assets, that install initially with the program, but it's pretty sparse. If you have several drop-downs, each with Menu Sets, in Create Menus, then you have all, or at least most of the additional Functional Content.
As to why the program might think that you have not installed this additional Functional Content, I cannot say.
Could this be the sales pop-up for Photoshop.Com (or whatever it is) with the "Plus" membership? That membership has a few items for download, but so far, the offerings seem to be sparse. I think that the Photoshop.com Plus is a US-only thing, but that might have changed. [Many felt that the Plus was a bit of a rip-off, as the number of offerings were sparse, seasonal, and the additional storage capacity not worth the $. Those feelings come from others, as I do not have such an account, so have not actually seen what is included in any Plus membership.]