Cannot upgrade license to Unity3d Pro 4.6 trial

I am not sure if i can’t upgrade to Unity Pro trial or if i already did this in the past and as a result of this license has expired.
I am following all the steps to upgrade the license:

1)Generating properly a license according to my serial number(https://license.unity3d.com/)

2)Loading the new license(Help->Manage license ->Manual activation->Load license)

3)Activating the new license(Help->Manage license → Activate new license)
Using the same serial number. After clicking OK, a “Please wait” message appears
and nothing happens. The Unity version is still the free version. Nothing changes in Help->About Unity, The Profiler is not enabled etc…

Any ideas?

Drop your issue into the support team, using the web-form on the Unity site. Give them your serial number, your the exact email address you’ve used for your Unity account. They can then help you out. If you’ve used the Pro trial before, then it’s not possible to use it a second time. Also, a lot of the Pro features are now part of the 5.x free version, so using 4.6 is a bit pointless.