Summary
while playing online co-op, few minutes after logging in the objects stop to be selectable. you cant high light, use or pick any item from the floor. no even the shelter is selectable so you cant save the game.
Steps
just enter the co-op, choosing any server and private visibility.
Extras
already tried to reload and clean cache.
Hi Pca123, welcome to the forums,
This interactions issue is one the team is aware of and are currently working on a fix for. You can find more information on the issue here: [Known Issue][PS4/XB1] Loss of interactions along with some workarounds players have been using.
And in case you haven’t seen it yet, Sam also posted an update earlier today here: [PS4/XB1] Dev Update on Interaction Bug
Edit: I should mention one workaround that might help with saving or interacting with some items is crouching and trying to highlight the lowest corner or edge. Players have found they can highlight the bottom of the shelter to save and in some cases standing right on top on an item and crouching may also help you select it. I understand this is not ideal but hope it may be of some help while the team continue to work on this issue.