Hi, how did you remove your credentials?
On your Add-on store, select the 3 dots in the top right of your screen, and go to “Registries”. You’ll be able to add/remove any credentials for container registries.
I had this issue with my raspberrypi 5, I solved it by adding the CloudFlare nameservers:
sudo nmtui
# add 1.1.1.1 to IPv4 DNS servers
sudo systemctl restart NetworkManager
Warning: using public DNS servers will stop .local (mDNS) addresses from working