Context:
Shatterline is the slightly better equivalent of old Source games with bad PC ports - while all Source games freaked out into kernel panics if you alt+tabbed with them running as fullscreen applications for macOS (Team Fortress 2 being quite the example), Shatterline freaks out and freezes into a black screen if you try and alt+tab when it is loading.

Testing:
An easy way to test this out would be to start the game up, and immediately alt+tab to a new window during the splashscreen with the weird minigun lady from the thumbnail. As long as you do not alt+tab back into the game, the game will stay frozen and will not resume playing the introductory video. Once you alt+tab back into it, the game will resume as per usual. This is the case under Fullscreen conditions.

Solution:

• Don't alt+tab immediately after a match ends, or you get unceremoniously kicked out of a PvE or a PvP server due to lost connection.
  
• If you do alt+tab in a loading screen, you do not have to hard-reset your rig's power. Instead, you can ctrl+alt+delete and sign out of your account, which will force all applications close. This is a quicker way to get back into playing a better polished game.

Context:
Given the early access nature of the game, Shatterline was bound to have server and login issues from the get-go. One of the issues is the inability to be able to be logged into the game's servers successfully, as a spike in player numbers can easily overwhelm any server, leading to some wacky ♥♥♥♥ when it comes to accommodating players that are logging in after the spike - like, way after. Yes, even sixty minutes after.

Testing:
When you start the game up and await the splashscreen to end, the loading screen starts up and hits you with a "Error: Connection Lost (01-00)". The only button present is "Close" - unsurprisingly enough, it closes the game completely. There is no way to change servers midway through login; my guess would be that your regional selection does not matter when it comes to being logged in, or the devs are yet to implement a feature where you can change your server at the start screen, making logging in much more convenient.

Solution:
When "Error: Connection Lost (01-00)" shows up, do ... nothing. Eventually, after an undefined amount of time dependent on the player strength of the game at that moment, you will be put into a login queue (represented by "You Have Been Entered Into A Login Queue. Please Wait." or something similar). TL;DR - DO NOTHING.