EDATE in excel help

Hello... I have a training for log for a large number of staff for various different courses which have all been completed at various different dates and I want to show the expiry dates for each entry in another worksheet. I am using the EDATE function (referencing back to a cell in another worksheet) to do this but it is returning an incorrect value. However when I use EDATE in the same worksheet it works fine? Please help, struggling with this one. Thanks in advance.

I also want to be able to copy this formula across but leaving the cell blank if there is no date entered in the original cell. I would greatly appreciate any help please, thank you for your time.