Hi @Sarahcion; welcome to our Community and sorry to hear about this.
It seems like the original file that the shared link (the one which your tinyurl is pointing to) has been deleted as the link now is giving a 404 error.
In that case, you can look at your deleted files page and restore it from there for the original shared link to function.
Alternatively, you can create a new shared link for the newly added file and generate a tinyurl that points to that shared link instead.
Keep me posted on your progress, Sarah.