W70B Access Denied

[PDGIT]

Hi !

I need your advice ...
For my client I have a W70B Dect, which in my office network, is correctly detected, and I can access to it with default password. (DHCP IP / I let the default password)

When I plug the W70B dect at my client office, i find it on his network, but when I try to connect with default credential, it's directly denied ...

It seems the credentials are automatically modified but how ?
If somebody has already encountered this problem, I'm lost ...

Thanks a lot