There are several .htaccess files in Mantis that you will need to port to nginx for the API urls to work. For example /api/rest/.htaccess.

@vboctor I think this should be documented in the Admin Guide, especially considering that nginx is listed as one of the supported web servers in https://www.mantisbt.org/docs/master/en-US/Admin_Guide/html-desktop/#admin.install.requirements.software

I opened 0032794 to track the documentation update.

Until then, I see no point in keeping this open. @administrator if you do get this to work under nginx, by all means keep us posted with details on how you achieve that, for the benefit of other users. Thanks !