I know there have already been multiple tickets for this issue, but all of them have either been closed referencing fixes in newer Versions or occur after closing the browser.
In my case, I just set up the whole environment a few days ago: KeepassXC + Browser Extension, syncing the database over google drive. In all browsers I use: Firefox (Waterfox) at home, Firefox (Waterfox) at work, Chrome at work, the browsers lose connection to KeepassXC after about a day. I kept the computers, the keepass applications as well as the browsers running all the time, i.e. no downtime throughout the night.

Expected Behavior

The Browser Extension should keep the connection, or, as long as the connected database identifiers still match, be able to reconnect.

Current Behavior

The extension loses connection, displaying the "KeepassXC-Browser has not been configured" message. In the settings under "connected databases" the correct connections keys are listed, they show up in KeepassXC in the database settings aswell. (Of course, different identifiers between computers and browsers, i.e. firefox-home, firefox-work, etc.)
Restarting the browser, KeepassXC or both does not fix the problem, only adding new connections through the extension.

Steps to Reproduce (for bugs)

It might have something to do with keeping the systems running for prolonged periods of time, but I could not yet determine when exactly it happens since the connection has usually been lost the next day.

Debug info

KeePassXC - 2.4
KeePassXC-Browser - 1.3.3
Operating system: Windows 7 at home, Windows 10 at work
Browser: Waterfox 56.2.8 (Firefox fork), Chrome 73.0.3683.103