If you get this error when activating, download the latest version. The online activation system was upgraded (see previous post) so old versions cannot read the keys it produces.
This is most likely to affect trial users upgrading as they are more likely to be using the old version.
Please do not send error reports for this error. As the error is before activation, I cannot tell who you are so cannot help you.
Similarly, “The input is not a valid Base-64 string…….” message is caused by trying to use an old format key file on a more recent version. (The wizard tells you not to do this)