Comment 9 for bug 1671205

hmm, so mongo exits with error, all params look just fine, can you check if you have folder:
/var/snap/wekan-ondra/79/share
and
/var/snap/wekan-ondra/79/shared

Also you can start mongo manually, to see if you get some error:
$ snap changes
find change corresponding to refresh to 79, then
$ snap change <change id>

What is your snapd version?
$ snap --version

If folder /var/snap/wekan-ondra/79/share does not exist, then create it and se if that fixes the problem

If folder exists, try to run mongo manually to get more logs
/snap/wekan-ondra/current/bin/mongod --dbpath /var/snap/wekan-ondra/common --logpath /var/snap/wekan-ondra/common/mongodb.log --logappend --journal --unixSocketPrefix /var/snap/wekan-ondra/79/share --port 27017 —verbose