I am having a similar issue using Zorin OS, on my first VMware installation I somehow got Enpass to link to my Dropbox sync location. It took allot of effort but I am unable to replicate the solution. I am able to install Enpass and log into my lifetime-pass account. Enpass then asks me to log into my cloud storage account, I do so, a web page pops up, in Firefox (I also tried Chromium) I log into my Dropbox account and hit the Approve button (twice actually-every attempt) Enpass pops back up and looks like it is trying to connect but after about 10 minutes it fails and says try again. I have checked my Dropbox/Apps/Enpass folder and verified that there is only one vault there. On Dropbox I tried deleting all my installed apps including Enpass and that didn't do anything more than log me out of my other linked devices. I also tried backing up my Enpass vault, copying it over to Zorin, loading a file in Enpass and entering my vault password, all my passwords become available. But I am still not able to connect with my online account. I also tried logging into Google-drive, with the same issue. I kind of assume that the browser isn't really passing the verification back to Enpass but I can't confirm that. It's most likely a permissions issue in Linux but I can't fine anyone talking about that online. I am currently making a backup of my 207gb, working VMware installation of Zorin and am planning to install it over the hard drive (MVMe) installation. Even though I assume that will work, I would still like to know why this process is so hit or miss.
Update: I found the solution. 1st uninstall the Enpass app from the builtin app store. 2nd install Enpass from the Enpass.io web site. just copy and paste each line below into the terminal one at a time, problem solved.
echo "deb https://apt.enpass.io/ stable main" | sudo tee -a /etc/apt/sources.list.d/enpass.list
wget -O - https://apt.enpass.io/keys/enpass-linux.key | sudo apt-key add -
sudo apt update
sudo apt install enpass