Viewer RT ''No Server Communication''

Hi,

I have 2 client PCs that running WinCC Viewer RT and a server that running v16 rt professional.

The problem is that the clients worked for 2 days at the beginning, and after that, i couldn't connect with the server through app but i connect through a browser (without showing any data cause it is not supported any more). So the connection between PCs and Server seems OK but Viewer RT is not working for both PCs. Any suggestion?

Best Regards,