That is becuse the licens string added was either for another serial number or you mistyped one or more chars.
If you have the excel file then in excel copy the license, go in manager, go to licenses add a new license and paste the license then mistyping is not the case. In excel on the far left it shows the serial number the license belongs to, check if it is equal to the license number of you system, you can find it in manager on the system/systrm page.
If it ain't dutch it ain't much