My daughter suddenly couldn't use the inventory anymore in Vivecraft, once opened. She couldn't pick or move items in there. The cause was that Vivecraft's window was not active on the PC at that moment.
Click to Read More
Vivecraft is a mod that turns Minecraft into an exceptional VR experience. Concretely, I use it to run the game from SteamVR and play with it using my HTC Vive pro setup (Be sure to setup and run the game as explained here. Launching the game from the VR Room or Steam does not work).
When my daughter experienced her issue with the inventory, I was working on the PC at the same time. Vivecraft works indeed fine if someone else is using the PC, as long as you don't need the mouse to interact with the game. And this is the case when you want to use the inventory or use some menus.
Concretely, on the screenshot here under, the cursor + will only appear if, on the PC, the window of the game is activated. I.e.: if you clicked on it with the mouse or used Alt-Tab to give it the focus.
So, each time my daughter want to use the inventory, I temporarily give the focus to the window of ViveCraft by switching to it with Alt -Tab. I can next continue to work...