No games using Proton work

**Game information**
Multiple games, including GTA5, Magicka and Risk: Global Domination.

**Distribution name and version where applicable**
```
▶ cat /etc/os-release
NAME=Gentoo
ID=gentoo
PRETTY_NAME="Gentoo/Linux"
ANSI_COLOR="1;32"
HOME_URL="https://www.gentoo.org/"
SUPPORT_URL="https://www.gentoo.org/support/"
BUG_REPORT_URL="https://bugs.gentoo.org/"
```

**Flatpak info**
```
▶ flatpak --version
Flatpak 1.4.4

▶ flatpak --gl-drivers
default
host
```

**Problem description**
Games that according to ProtonDB work as Gold or even Platinum just fail to launch for me. This includes for example Grand Theft Auto 5, Magicka and Risk: Global Domination. In case of GTA5 it tells me to check the game data, in case of Risk: Global Domination it just closes/crashes after the initial loading popup, and in case of Magica it crashes without ever showing any window.

**Does this issue reproduce with native Steam**
Have not tested and I can not since this is a purely 64-bit system.