In terms of viewing your alerts at https://www.elitetrader.com/et/account/alerts the setup is as follows:
Unviewed alerts don't have an expiration, but previously viewed alerts will remain for 4 days and then they expire and disappear.
The settings haven't changed at all. But maybe when you were gone for two weeks, a lot of alerts that were previously viewable became expired. I'm just guessing on that though.
You can says it is a change. Policies revert all the time,Anyway, seems to be a permanent change rather than a glitch.