It may be because the reviewer suggested a retrial or the editor-in-chief thought that the reviewer's comments were not good enough and asked for a retrial. Because even if the reviewer suggests accepting your manuscript, the final decision is still in the hands of the editor-in-chief, and it is normal to have a second or third round of review. It is also common for editors to ask for additional review.
However, this does not mean that the manuscript is rejected, because the journal editors and reviewers are very busy and will not spend a lot of energy to reject the manuscript, but directly reject it. I must have seen the value of the paper before I wanted the manuscript to reach the level of publication.
So you can continue to wait patiently and wait for the paper to be accepted.