Change of internet provider

Hi everyone,
I activated the FTTH service with another provider and I can no longer connect with my NextBox which I had configured via the “Guided Dynamic DNS” with
I guess the problem is the loss of the connection with the IP address of the router but I don’t know how to do to solve the problem. I can access to my nextbox/nextcloud with ssh only.
Someone could kindly help me?
Thanks so much!

After some work, now I can access also via web interface to my nextcloud but why in NextBox->Remote Access->Network Information I have:
Using IPv4 address:
Using IPv6 address: 2a02:29e1:504:d601:39f5:6ce:bd62:54cd
that are my old and no more used IP addresses!
For clearence, some days ago I de-configured the “Guided Dynamic DNS” and I tried to reconfigure another one with my new public IPv4 and IPv6 addresses but no one of they was reachable (yes, I followed all nitrokey’s guide and raccomandation).
Today I find theese old public IP: why? Are they upgradable with some cli command?
Thank you a lot for any help.