Hi Dominique

This looks as though it is possible to activate users using the Upload users csv with the suspended column and the Allow suspending and activating accounts turned on.

Full details of the fields and how to do this are detailed in https://help.totaralearning.com/display/TL9/Upload+Users#UploadUsers-Fieldsthatcanbeincluded 

I think the value of 0 in the suspended column will activate the account. Try this out on a test account to see how this works.

regards