Sketchup School Design Not Saving

I was finished with my work, I was ready to save it. I clicked on save, It failed to save. After, I reloaded the page and it was gone. This is my project and it is due today(it is 8pm for me). After that, I made a new design. I was again, ready to save. Same thing happened. I changed the file name and saved. It changed back to untitled and it is currently stuck at saving. I tried to save it to my computer. It downloaded and saved. When I uploaded it to google drive, I opened it. In the sketchup loading screen it says “This is not a SketchUp Model!” Please help me. This is 60% of my grade. I need help.