There seems to be a problem with Twitch drops on consoles
IF the ESO account once migrated to console from PC.

I once started playing ESO on PC and later officially migrated my account to PS4 when this option was available on PS4 release. Today, after linking my Twitch account to my ESO account and watching a Twitch stream, I indeed received an email from ZOS about getting an Ouroboros Crown Crate, telling me to find the crate after login to in game. However, after login on PS4, I found no Crown Crate at all. Therefore, I assume the crate was assigned to my old PC account which I did not use for years. As a workaround, I tried redeeming the code that also was given in the email on PS4, but I was told I could not use this code.

ZOS, how are we supposed to get the crate on a migrated PS4 account
if the old (an unused) PC account probably still exists?

[EDIT]: The problem is gone - I now receive the Ouroboros Crates on PS4.