After changing the ‘Confidence Threshold’ to ‘40’ (the Face I uploaded was not of the greatest quality (Detection Quality = 43,75)) and restarted the Face++ app, it seems to work.
Although not sure what exactly fixed the issue (I think it is the combination of the new faceplusplus.com account and the fact I uploaded at least a single Face) it is working. Hopefully this helps others facing similar problems.
Robert.