Is it possible that the unused machine has the wrong date? Perhaps that confused the operative system file dates and Dropbox.
(I have an old machine that hardly use now that has problems with the motherboard battery and sometime it travels in time to a funny date like 2000 and all the security certificates are marked as wrong.)
(I have an old machine that hardly use now that has problems with the motherboard battery and sometime it travels in time to a funny date like 2000 and all the security certificates are marked as wrong.)