Under the following assumptions,
- there will eventually be a quarter round or other trim strip to cover the gap between the laminate material and the existing trim around the window (which will help hold the laminate in place regardless of if it's clicked-in or not
- this isn't likely to be a high-traffic or high-stress area for your flooring material
- you just can't get it to click, even after you've checked that the groove is clean and you've tried using a pull bar and/or a flooring hook
My next step would be to use a wedge-shaped shim between the board and the wall of windows, as a way to help your hammering/pulling force get directed in the right orientation.
If that doesn't work, as a final resort, I would just cut the groove off the short end of the piece (but leave the finished surface intact, and leave the groove on the long edge intact, since it seems to be seating correctly) and slide it in place so it's flush without that gap showing. With no groove, you should be able to butt the finished surface up tight without having to force anything to click. The quarter round (or other trim) will hold it in place well enough. If it does move enough for the gap to reappear, you can tack that one board in place with trim nail(s) hidden under the quarter round.
An advantage of floating laminate flooring is that when you have a challenging spot like this, you can try something out - and if it doesn't work, just replace the board and try something else - all you've lost is a few minutes of time.