Login attempt or request with invalid authentication - token issues?

I have two laptops on the same network, one which is routed through a corporate VPN and the other is more directly connected to internet.

Everything works as expected from the “directly” connected laptop.
I can not login to HA from the VPN-routed computer, regardless of which of my users I try to use I get a notification and a log entry. The IP-address is the ISP-assigned address to the router, thus the same for both laptops.

Login attempt or request with invalid authentication from 147.XXX.YYY.98 (147.XXX.YYY.98). See the log for details.
Logger: homeassistant.components.http.ban
Source: components/http/ban.py:138
integration: HTTP (documentation, issues)
First occurred: April 24, 2024 at 17:49:25 (13 occurrences)
Last logged: 08:45:52

...
    Login attempt or request with invalid authentication from 147.XXX.YYY.98 (147.XXX.YYY.98). Requested URL: '/auth/token'. (Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/121.0.0.0 Safari/537.36)

No http-ban file.
Login works from the “direct” laptop, so username and pwd verified ok.
External access to HA provided via the thirs-party cloudflare plugin, it works well for all other clients but the VPN-laptop.

Core: 2024.4.4 and OS: 12.2

Any help welcome.