Please provide some more details.
Are you using a CC subscription or a stand alone license?
What is your OS?
What steps are you taking and do you get any error messages? If so what are they??
Hi erlingp ,
Which version of Lightroom are you using?
What is the exact error message when you try to update?
Refer Keeping Lightroom Up-to-Date and download the update patch for the version of Lightroom you are using.