Hello Monjilla,
Welcome to Apple Support Communities!
We want to help so you can upload your videos without issue again.
This Apple Support page has the full steps to take for when Safari doesn't open a page or work as expected: If Safari doesn't open a page or work as expected on your Mac - Apple Support
Start with:
"Reload the page
From the menu bar in Safari, choose View > Reload Page. Or press Command-R.
If Safari doesn't reload the page, quit Safari, then try again. If Safari doesn't quit, you can press Option-Command-Esc to force Safari to quit.
If Safari automatically reopens unwanted pages, quit Safari, then press and hold the Shift key while opening Safari. Learn how to control which windows Safari automatically reopens."
Or if the issue is isolated to TikTok, try the steps here to help with their software or reach their support as needed: First steps | TikTok Help Center
We hope this helps to further isolate the source of the issue so you can resolve it.
Please let us know if you have further questions.
Cheers!