Hurdles may come in many forms and shapes. Here is a list of some of those,
1. Your research question could be either not enough interesting, OR not enough well explained to the reader. "Interesting" means, for example, that it is ORIGINAL, and that it expands knowledge enough.
2. Whichever field you are in, writing a COMPLETE paper has certain meanings, and there are always some items that you cannot be without, regardless of which field of science you work in. Here is a link to a paper I wrote with a colleague on the most important things to think about:
For example, your paper needs to answer an actual research question, and it needs to be one that more researchers than you would be interested in reading about. It therefore cannot be too narrow or be written in a too complicated way.
3. You should probably present your work to your colleagues before sending the resulting paper, so that you get feedback that may improve the presentation of your results.
4. There are guidelines on how to write good papers. I usually refer my new PhD students to a very good book in the writing of mathematics - "Handbook of Writing for the Mathematical Sciences", by Nicholas Higham, published by SIAM. Here is a link: