Finally I've fixed it uninstalling the current driver version marking the check optin "Delete the drivers from disk" . Doing this, magically now is working. Also I've had to prevent Windows Update to update Dell Wireless broadcom again. If driver is updated, the problem comes again. Thanks to all for your suggestions. 
Dell XPS 13 9343. I've upgraded to Windows 10 and WIFI worked fine. But after the first update installed from windows update center, WIFI is not working. In the device manager (Dell Wireless 1560 802.11ac) it appears a yellow warning on it. And I have the latest version of drivers installed. Fololling the advises from other posts, this is what I've tried (without success) so far: 1) Re-install the drivers manually 2) Run command reg delete HKCR\CLSID\{988248f3-a1ad-49bf-9170-676cbbc36ba3} /va /f  (register entry not found) 3) Run command netcfg -v -u dni_dne (dni_dne not installed) 4) I don't have installed any Cisco VPN Client Any ideas?  Thanks in advance for the support
XPS 13 9343 No wifi after first update of Windows 10