Too many activations

I own Acronis TI 2014 Family Pack (3 PCs) which is installed on 3 PCs in my home, all with the same serial number.
In December I was offered an additional license which I purchased.
This has a different serial number.
However, when I installed this on an another PC ,using the new serial number, I get a "Too many activations" message. I have not installed it on any other PCs.
I have re-downloaded the install file from the Acronis website, repair installed that, but when I try to activate it, still get the "Too many activations" message.

How can I get out of this loop?

Thanks

Chris