[Users] Offline?

[Peter Wiehe]

I get the following error:
---begin of error message
Claws Mail needs network access in order to get mails.
You're working offline. Override?
---end of error message

But I have normal access to the internet. If I click override, I can
fetch mails without trouble. Also I can surf the web without any
problem.

What does this error mean?
How can I get rid of it?

I have the following configuration:
IMAP
Claws Mail version 3.17.5
GTK+ 2.24.32 / GLib 2.64.6
Locale: en_US.UTF-8 (charset: UTF-8)
Operating System: Linux 5.4.0-107-generic (x86_64)
Ubuntu 20.04

Greetings
Peter Wiehe