Why is my paper constantly being rejected despite supervisory team being very happy with it?
This can happen when a paper is sent to the wrong journal.  This may often happen with an inexperienced researcher.  A Ph.D. student normally could get advice from the advisor on which journals to try next.  When there is no one &quot;very involved&quot; with your research area to advise you, what to do?
Look for journals that have recently published papers on topics similar to yours.
After being rejected from a top journal, try a less prestigious one.  In the future, after you have more experience with publishing, you will be better able to judge what level journal to send your papers to.  But also note: if your papers are always accepted by the first journal you send to, then you are aiming too low.