Hello djahid rerb
Welcome to Microsoft Q&A Platform, thanks for posting your query here.
Error "the host does not exist" indicates that the FQDN name you are trying to use and connect to VM is not configured.
Make sure you have created fully qualified domain name for your VM correctly and then try to connect to the VM.
Ref: https://learn.microsoft.com/en-us/azure/virtual-machines/create-fqdn
To cross check I would also recommend to try connecting to VM using Putty via Public IP. If this connection fails, try to check if the Public IP is accessible on port 22 using this link(https://ping.eu/port-chk/). If this is closed then make sure the NSG has the port 22 allowed.
Hope this helps.