Most of us find the cloud all too nebulous. When it plays up – services strangely vanish, or you have to keep logging onto the service – there seems nothing that you can do, unless you have the patience to contact support.
In fact there is quite a lot that you can do to work out whether it is your Mac, your internet connection, the internet more generally, or the cloud service itself, which is at fault.
First decide whether this is the only internet service which is playing up. If many or all websites are down and there appear to be more widespread connectivity problems, then you must next rule those out as a cause. Sometimes internet outages affect some protocols, such as HTTP (web) or HTTPS (secure web), but not others: those are often located in your ISP’s central systems, where different paths may handle different types of traffic. Sometimes these may be reflected in your ISP’s service status page, which is always worth a quick check.
Next open Console and watch its logs when you try to access the affected service. Although the messages there are hardly in plain English, you may be able to understand enough from them to work out whether the problem is in your Mac, or is remote.
If it looks like the problem might be in your Mac, the best thing to do is to restart in Safe mode, with the Shift key held during startup. This flushes various system caches and should give OS X the best chance to establish connections. Except that Safe mode also disables third-party extensions, on which your service might depend. It is useful to know whether the service in question does run normally in Safe mode first.
Another good place to check is the service status page for the service which you are trying to access. In case you did not realise it, all the major cloud (and similar) providers have service status pages, some of which provide very fine-grained detail. Here are some links to those which you are most likely to use.
Is It Down Right Now? is a useful compilation of information gathered from users for various social media and popular web services.
Inevitably, a green or normal status does not mean that there are no problems, but that the service engineers are not aware of any. Most of those pages include support links, to which you can report your problems. This may seem a waste of your time and effort, but it is often the only way that the service gets to know of issues, so if you can, please report.
There is usually little point in trying to use Network Utility (or other general network tools) to try to check whether your connection to a service is good, perhaps using Ping. Cloud and similar services use large and complex networks of servers and routers, to which you generally have no direct access. Pinging http://www.apple.com will tell you precious little about connections with iCloud, for example. If there are internet trunk problems, sometimes Traceroute can be useful, but you could easily be looking at entirely the wrong destination server address, which may even be in the wrong country.
There are also lots of things that can affect your use of a service, which will not normally be reflected in the declared service status. So when you keep having to enter your Apple ID and password, iCloud may apparently be working normally. That’s where it does all get more nebulous.