Windors 10 activation error is one among the known issues, show up after the installation. A message pops up saying Windows 10 could not be activated. You also get a number of activation error messages which are reported to be quite common.

Here are some of the most common activation errors in windows 10, and a few things you can try to fix the problems that are causing them. 
Check out the following list which contains error codes and possible fixes for each error:

If you have upgraded to Windows 10 for free from Windows 7.1 Service Pack 1 or, Windows 8.1, but reach a non-activated state, perform the steps below.
Go to Start menu>> select Settings>>Update & security > Activation
Select Go to Store and check if a valid licence is available for your system. If not, you will need to buy Windows from the Store.

This only applies if you have not made any hardware changes to your PC.

Error 0xC004C4AE - 'Genuine validation detected tampered Windows binaries':
You get this error message if you have used a third-party app to add a display language that isn't currently supported by Windows.
The fix is quite simple: restore your PC to an earlier setting to undo the changes made in Windows. If you are still having the activation problem, it suggests your Windows copy is invalid and you need to buy a new one.

Error 0xC004F061:

This error means a previous version of Windows has not been installed on your PC, before you tried using a product key to upgrade to Windows 10.
You need to install Windows 8 or 7 before you perform an upgrade to Windows 10.
Error 0xC004FC03 – 'A networking problem has occurred while activating your copy of Windows':
You get this error if your PC is not connected to the internet or, firewall settings might be preventing Windows from completing the activation process.
Ensure that you have a stable internet connection and your firewall is not blocking Windows from activating. If you still see the problem, try activating Windows using your phone.
Error: 0xC004C008- 'The activation server reported that the product key has exceeded its unlock limit':
This error happens if the product key has been used on another PC, or, is being used on several PCs, which the Microsoft Software Licence Terms do not allow.
A simple fix is just to buy a product key (from Windows Store) for each PC to activate Windows. To buy product key from Windows perform the following;
Go to Start>> Settings>> Update & security>> Activation
Select Go to Store and follow the on-screen instructions to buy Windows
You can purchase product key from retailers as well.

Error 0xC004C020- 'The activation server reported that the Multiple Activation Key has exceeded its limit':

According to Microsoft, this error displays when a Volume Licence has been used on more PCs than the Software Licence Terms allow. The Volume Licence is one that is bought from Microsoft by a business to install Windows on multiple PCs.

A fix for this is to use a different product key to activate your PC.

Error 0x8007232B- 'DNS name does not exist' and error 0x8007007B- 'The filename, directory name, or volume label syntax is incorrect':

If you are activating your work PC but not connected to the network of you workplace, then you will find this error.
If you are connected to your network, and having this error, change your network settings.
To enter your product key, follow the steps below;
Go to Start menu>> Settings>>Update & security>> Activation
Select Change product key and enter the 25-character product key
You might need to enter an admin password or, to confirm your choice.

Error 0x80072F8F- 'A security error occurred':

If the date and time set in your PC are incorrect or, Windows is having an issue connecting to the online activation service and failed to verify the product key, you get this error message.

To verify your PC's date and time;
Navigate to Start>> Settings>> Time & Language >> Date & time
To check the internet connection;
In the search box on task bar, enternetwork troubleshooter, selectIdentify and repair network problems. Now follow the on-screen instructions to fix the issues with network.
If the network troubleshooter does not have any problem, then try to restart your PC, which will fix the issue.

Error 0xC004E003:

A third-party software that changed the system files should be blamed in such situation. Windows activation needs the system files and changing them will hinder activation.

You need to restore your PC's system files back to an earlier point. However, doing so will remove the software that was installed, without affecting your personal files.

Error 0x80004005- 'Unspecified error'

If this error message shows up, go to Start>> Settings>> Update & security>>Activation>> select Activate Windows to manually perform the Windows activation.
If it fails to work, restart your PC and then perform the activation. 

Source: http://www.teclius.com/2015/10/windows-10-activation-errors-and-how-to.html?m=1

Upgrading to Windows 10 has been smooth for most of the users, but some are also found reporting that there are encountering issues. Whether it is the screen flashing, not being able to connect to Internet, or the battery draining instantly, or upgrade errors this latest OS is having bugs and needed to be resolved the issues quickly.
There are many common and annoying issues that users are encountering in Windows 10, with the easy steps to fix them.

To know about various Windows 10 errors visit this: https://sites.google.com/site/troubleshootwindows10problems