That's a shame. The project looked interesting. Yours is the first report of that issue, which hints that's it's confined to your PC. If possible, test the program on another machine.
Just retested your 13 files. Caching all took about ten minutes. Though lengthy, they are low resolution and should be no problem. Additional files could be added.
Video editing is resource intensive. An I5 processor (or AMD equivalent), 8GB RAM, a mid-grade video card and ample free disk space on C:\ are advised - especially for high-def or big files. If C:\ space is limited, direct the cache files to another drive with more capacity, if available. OPTIONS | DISK tab.
You initially mentioned that you could not load "the video project file I already made." If you saved that project, as is prompted when exiting VP, please upload the folder that contains all its source files and the VPJ control file. Add the six missing files + the VPJ to those already uploaded.
Similar to what you did before, zip those files and upload them to a free server like Google Drive. Make them public (shareable) and copy the link. Post it here. For Google, be sure to change 'restricted' to 'anyone can view.' Someone will be glad to help you.
If all is in vain, you may be able to get a refund... https://www.nch.com.au/general/refund.html
