error unable to install the Add-on

Hi, I have the Creative Cloud membership.

I just re-installed the CC on a new computer (iMac).

I keep getting the message

“Unable to install the Add-on ID imposter Trial (error -603) (referring to Indesign, but the message comes up regularly).

As I don’t have the Add-On because it was only a trial, I have nothing to delete.

I have already looked at all the information on Add-ons. It does not mention this problem.

How can I stop this message appearing?

Thank you,

Mac 10.9.5 Mavericks, 32G ram, iMac27 3T HD