I am still getting the same error as in this thread (however, that thread was closed).
Version issue: update the server. The API is not compatible with this plugin version. Your passbolt administrator need to update passbolt backend to use the latest API version. API: v1.6.10 / Plugin: v2.0.8
Browser: FireFox 60.0
That thread suggests, that the issue is fixed with the newest 1.6.x version and the newest extension version - however I am still experiencing this. Is there no other way, other than updating to 2.x?