Might help if you indicate what you tried and what version you had that you were trying to upgrade from.
I have sql server express backend and got a message today that Lansweeper needed updating. downloaded the update and am now running v6063 if that is of use to you.
I am sure you checked that you have access to the database, that it was running, and that you had run the exe as an admin on the iis box?
By chance, anything in the event viewer?
open an administrative command prompt, cd to the folder where you put the download, run lansweepersetup /? and there is a list of command line parameters it supports.
the interesting ones might be to LOG and CLOSEAPPLICATIONS just by chance.