Hi Paul...thanks for your question. It appears that your employer used his/her Microsoft Volume License keys to activate the software on this laptop. The problem with that is that volume licenses are not one-and-done activations...they require an ongoing connection to the volume license server at the business location in order to stay active. The following explanation comes from Microsoft's volume license website:
"After the client successfully activates, it attempts to contact a KMS host once every seven days by default to renew its activation another six months. Each client has a six-month countdown timer that resets whenever the client renews with a KMS host; if the client can’t renew for some reason, the timer keeps counting down, attempting again every week, until the client either renews or falls into the Unlicensed state."
In your case, it sounds as if the end of your six-month activation period is expiring. Since you no longer work for this company, the activation server is inaccessible by you and so your copy of Windows is failing to reactivate.
To fix this, you will need to obtain a valid retail "key" for your installed version of Windows. This will cost money (which stinks, I know), but far less than buying a laptop...so it's still a nice gift! If you might let me know what version of Windows you have installed, I can help point you in the right direction so far as how to make this purchase.
Another option you have is to contact Microsoft at their piracy reporting website, which may net you a heavily discounted license, but may result in your employer getting into a bit of trouble for using a volume license key to activate your copy of Windows. Probably not desirable, but it is a legit option that is available to you.