WORKED FOR ME
I read through 9 pages of comments, like others. What a broad selection of non-helpful suggestions.
The fix for me was to go to user accounts in control panel. Then select Change UAC settings, next move the slider down to the second notch from the top, then "OK".
Go to PC Settings, Network, Connections. Select your connection. Amazingly, the FDandC slider is now visible. Turn on.
Now go to Network and Sharing Center. I see under "View your active networks" that my network is marked "Private"
Also, in NandSC I can select "Change advanced sharing settings" and it shows the current profile is Private and I can edit settings for profile types.
This, on the face of it, implies that the problem of the "missing FDandC slider" is fixed for me.
For fun, I can go back to UAC and set highest level. Then, go to PC Settings, Network, Connections. Select your connection. Wow, the Slider is missing again.
I can adjust the UAC back down again and the Slider re-appears.
I have no idea how this works. I can see no reason for a correlation between UAC level and the slider appearing and disappearing. But it does exist (but only on certain systems). I will qualify the statement by saying that this correlation must only exist
on Win 8.1 systems that have the "disappearing FDandC slider" issue. The specific PC I am working on now is the first that I have seen with this issue.
On all other PCs that I have worked on, you simply go to the network connection and move the slider to change the profile type (as suggested by several good-intentioned posters) If you have not personally experienced this you probably believe the various
previous posters are stupid not to just move the slider. For the previous posters part, (and mine as well) We think the various responders are dumb as a sack of hammers to not see that people are screaming "but the problem is that the SLIDER IS NOT THERE!"
Many responders did not read the statement "the Slider is not there".
Making the Slider disappear and reappear is a reproducible condition, but (in my experience) only on the few PCs that have been affected by the "disappearing slider issue". This set of PCs is at least big enough to support this long-running thread, as well
as others on different blogs. The "adjust the UAC solution" may only work for a subset of the "disappearing slider issue" set. As I said, this PC is the first I have ever seen with this problem.
Until some smart person can figure out what causes the "disappearing slider issue" in the first place, there will not/cannot be not response from Microsoft. They must see a PC, with this issue, with their own eyes. The occurrence of this issue is rare enough
that this may not happen soon, if ever.
I feel sorry for those who have wiped their PCs, moved their profiles, or performed other radical procedures suggested in the previous nine pages.
Even though I have had the experience outlined above and was able to apply the fix suggested by the poster to fix the issue, this is work around at best. It requires that you reduce your UAC security level to work around the issue. I can bear it, but some
won't.
It is clear to me that the problem is real, if only for a small set of affected users. We may never know.
It is kind of creepy that the poster above suggested that this has been seen with Win 10 too.
Goodnight, and Good Luck.