There should be options on the Help menu for Update Your Sage 50 Product and Update Service Plan?  There used to be an option to Unlock Payroll but that may have changed over the years.

I've never had to use them but they might be what you need.

However, when you get that second message you posted, usually that has to be unlocked by someone at Sage.

Thank you Richard. It has finally been resolved after re-dialling into sales, as oppose to support. Their Support recording would refer me to my Portal, but nothing I tried worked. Eventually, a Sales Agent issued me a replacement Serial # and Key Code, and she was able to activate that one. 

It was rather odd, since my profile and purchase history clearly listed my purchase as activated, but it wouldn't function.

The past 3 years,  my activations have required assistance, since the software refuses to fetch my active key code and authorize my purchase.   Kim