Sketchup Pro 2015 Not Activating

I manage Sketchup Pro 2015 licences for 15 users, and we have just updated them from Windows 7 to Windows 10 machines.
I have removed the licence from the old machines, and I am trying to activate the licences on the new machines.
8 activations have been successful, but the other 6 licences/installs will not activate.
I enter the serial number and activation key, and click Activate - an NOTHING happens, not even an error message. It’s like the activation button is just not working. I close the program and try again, same thing, it just sits there.
Any advice?

There is a problem we’ve been trying to fix for a while. I will send a direct message to you, to get some information I will need in order to work around the problem.

Hi, I am having the same problem for Sketchup Pro 2015. Please help.

Hi, i have the same issue. Is there a way around ? Thank you.

Hi Colin, We have the same issue, can you please assist us ?

Dear Colin,
I have a same issue with reactivation of Sketchup Pro 2015 full license on new computer.
I would appreciate a lot a hint how to make the activation work.

Thank you in advance