It sounds like the desktop is crashing. What hardware are you using? Specifically, which GPU and which drivers? What Pop OS version is it, the one based on Ubuntu 18.04 LTS or the 19.04 version? Are you using any PPA's for updated MESA drivers? More information is needed to give any specific help.
I Had a similar issue, not specifically with that game but on another (SWTOR), other games were working fine but it would drop me back to the pop-OS log in screen.
Your issue may be different but after much testing & asking a friend to load the same settings I had onto one of their machines, with them getting it to work, I started to look at what was different between our machines.
What I found was causing it was having a CPU with onboard graphics & a D-GPU running at the same time (this was possible in Windows using Lucid Logics Virtu software but apparently not Linux). It was an easy fix in bios to set the D-GPU to on & the onboard graphics to off, once I did the game performed as expected & no more crashes to Pop-OS log in screen at loading.
If you have a CPU with onboard graphics, that may be your answer.
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