ok,
After searching deeply on the forum, I’ve found some useful informations.
firstly, the command to enable or disable IP access restriction was not good. it is:
sudo yunohost settings set security.webadmin.webadmin_allowlist_enabled -v False
and not
sudo yunohost settings set security.webadmin_allowlist_enabled -v False
So, after tyming the right command, I’ve been able to access webadmin again.
Then, I noticed that I hadn’t put the IPv6 ranges in the authorized addresses.
After doing that, everything went well.
Sorry for the noise.