glad i could help llya
You may also have to click "Bring to front" if you have other windows open such as your browser
I'm having the same issue, I found a work around so that you'll at least be able to play. If you open your task manager and right click the minecraft launcher a drop down will appear. Click "Maximize" and you'll be able to open the launcher in full screen.
Hope this help and have fun creating and surviving 🙂
It seems as though a recent windows 10 update has removed the maximize feature from my task manager so now my own fix won't work for me 😞