Aeroccino deosn't make froth

Our aeroccino worked fine for 2 years and suddenly it didn't made foam anymore. We tried the "inverting trick" without much success. We contacted Nespresso and they suggested switching from regular fresh milk (we used 2%) to UHT milk (harder to find in US) and to use it cold and freshly opened. So we tried that and it works.
Hope this solution works for you too

Try a better quality whole milk. Most of the milks available don't froth at all in mine. Good quality fresh whole milk froths very well. Low fat milk froths fairly well, again, only high quality milk. Skim doesn't froth at all. Experiment a little. I think many of the milks available are over-processed, or composed partly of reconstituted milk that won't froth naturally. Good luck.