If your project is not getting saved and there is an endless loop of "Saving Project" then here are some of the reasons why your project is not getting saved:
1. The names of the files should be smaller: Check the name of all the resources (files) that you used like images, audio, videos, flash SWF file, etc.. Make sure that their names are smaller and it should not contain any special characters like -, (, ), etc. Rename all the assets and then add and retry saving the project.
2. Image with very high resolution. Try a normal 2k resolution image like 1920 x 1080px.
3. Image, SVG, SWF, or Audio File size (MB) is too large. You can try a smaller file size and see if your issue gets resolved.
4. Faulty assets that you have added. In that case, remove the faulty asset/s and try saving again.