Parents IP address blocked in my Yunohost

My YunoHost server

Hardware: x86 Mini PC
YunoHost version: 11.2.12
I have access to my server : Through SSH | through the webadmin
Are you in a special context or did you perform some particular tweaking on your YunoHost instance ? : no

Description of my issue

I have strange problem. I have my Yunohost server stored in my apartment with Dynamic DNS handled both via Yunohost and Gandhi. I sometimes visit my parents and use my services. It worked fine for last 2 years but something strange happened about 2 weeks ago. When I connect to my parents WiFi I can’t connect to my services. It works when I turn on VPN (Mullvad) but when I am using network normally it does not work. I tried to change parents IP address by restarting router but it is getting blacklisted again. And yes, It does look to me as some automated job that blacklisting parents IP (Parents use Orange Funbox)

How can I diagnose this issue and whitelist parents IP addressess (as they are dynamic too)?

What app clients are trying to connect?
What devices are there?
What communication apps do you have : Nextcloud, mattermost…?
I had a similar issue with a mattermost client trying to connect with wrong credentials, I had changed the user password for it