windows movie maker

Hello

I had used windows movie maker last year for a video I made and uploaded on youtube so when I tried making a video today on windows movie maker it let me make my video yet when I pressed the save project button so that it can save properly and become an actual video to upload on youtube it didn't let me and told me to buy the full version software! I am really disappointed and confused as to why it's making me buy the software whereas this didn't happen to me last year, please help me with this issue as I am planning to make more videos with this app, I have no problem with the app itself as it is really fun and I understand how to make my video, yet when it comes to saving there's a problem.