JD-EE
"Why in heck didn't they hear the last few calls from ATLANTICO?"
The assumption is the crew selected SELCAL watch the moment they confirmed the SELCAL check with ATLANTICO.
The real question should be, "Why didn't ATLANTICO SELCAL them when receiving no reply? The controller would have had the code keyed in, and needn't look it up and key it in again.
I suspect the controller got busy with something else and thought he'd SELCAL them prior to TASIL with their transfer instructions. Did he try doing that? I don't know, and maybe as they were already on a virtual flight plan, he just let them go, and in doing so passed the problem to DAKAR.
mm43