Hi, here's an update and some insight:
There's two scenarios that could fall into this issue. The first one being that people use the steam version of the game and log into the epic account from there, in this case earning epic achievements does not work as it will only unlock the steam one. Fixing so you get both can get a bit complicated so it's been low priority to avoid breaking other things and disabling the achievements view in the epic overlay on the steam version doesn't seem to be possible unfortunately.
For the second scenario where you are using the epic version of the game you should be getting the epic achievements but it seems not to work in some cases for unknown reasons. We've been trying to figure out when and why this happens but have not been able to do so, making fixing it difficult. Epic works different in this case compared to steam where you need to be currently logged in at the moment of unlocking the achievement, which might not be the case if you are having this issue. As a general case if you get signed out from epic due to losing connection or any other reason there will be a silent re-log attempt the first time to re-establish connection, if this one fails you should be getting a popup telling you that you've lost connection asking if you want to log in again. Some info that could help us here is if you see this popup telling you that you've lost connection or if you might be doing something that might break the login for any other reason.
