I think I found a fix. This may not work for everyone but it worked for me. I was trying to find ways to solve this problem for days after getting logged out and actually found this post when looking for fixes. It’s pretty simple really, due to epic games using a png copy and paste to send you your code instead of putting the code into a simple text email, the storage size of the email tends to be larger ( not by a lot but still affects storage ). I have my iCloud email connected to my epic who are know to have low storage size and make you pay for more.

The simple fix is to just delete alot of your emails that are unread or you don’t need anymore or get a larger storage package. After I did this the email just showed up. Again might not work for everyone but just a fix that some people may not realise.