These days most tech companies are devising ways of syncing data between their devices and PCs. There are many ways of achieving this aim and most methods work without any issues of note.
Sometimes, however, problems do crop up and iCloud sync problems have been known.
The chances are, though, that the problem is not actually on the iCloud end. In reality, it is more likely that a device or internet connection is not working correctly. It could be that case that information and files are getting synced to some of your devices but not all of them. Worse, it could be that none of your devices are getting synced and this could be for one of many reasons. Perhaps some of your devices are on and working properly but they are not getting a good internet connection.
For a device to sync with the iCloud it has to be able to connect to the internet. Poor internet connectivity is therefore quite a problem and it will affect more than just syncing, leading to a general all round poor performance. A poor internet connection is actually the most likely cause if you are having iCloud sync or other problems and should be the first area you look at and attempt to troubleshoot.
Or it could be that some of your devices may be faulty and this is why certain features may not be working as they should. Again, try and discover the issue here by troubleshooting, checking your devices in turn, rather than assuming it is a problem with the iCloud itself.
If you are experiencing iCloud problems that you cannot solve on your own then there are many places you can turn to for help. You can search for online forums and blog posts but, perhaps, the best option would be to check out the Apple iCloud community first.