Hello gretianiomoni
Can you please check and confirm if the Windows Update service is Running?
You can do so by typing
SERVICES.MSC in the Cortana search box, opening the
Services snap-in and checking the Windows Update service from there. Please make sure to double-click the service and confirm if it's status is Running and its Startup type is set to Automatic.
If that doesn't help, you can
Boot Windows in Safe Mode, go to the
C:\Windows\SoftwareDistribution folder, delete all the contents from the folder, restart PC in Normal Mode and then try checking for updates.
Please report back if further assistance is needed.