I have an old copy of Elements 12 and have the License Key also. Installed on computer and won't allow me to activate. Makes me login with my Adobe account, Thens sends SMS code to my phone I enter it and it says connect to internet. Computer is connected to internet as I'm making this post from that machine.
Suggest that you call again and perhaps the functionary that answers will be more accomodating. Explain to the agent that you do not require help with the use of the software, just with activation. Be persistent and request escalation of the call to a supervisor, if necessary.