Desktop client Windows : unable to connect at first use

After installing on W10 the 2.5.3 Windows desktop client :
the first launch of it, it asks the NC16 server address : ok
then ask for “connect” : click on “arrow” : ok

then it asks for name and password : I type these.
(the same that have been successfull with Android client ou web interface client)
then : no more action !
the “Next” button stays gray.
the “Connect” button has no effect at all.
Something blocks the connection to server.
At these steps, I have no access to F12 logs on Windows desktop client.
I don’t known what to do.

Has anybody any idea to help me ?

Hello, non more problems since 2.6 Windows desktop client.