diegoc if other Flarum tables like users and discussions exist but migrations doesn't, something has gone wrong during the initial Flarum installation.
If that's the case, I'd recommend re-installing Flarum. Verify no error happens during installation.
Missing database tables could be caused by the PHP execution time being too short or PHP memory limit too low during installation, which might stop the install script very close to the end.
If some database tables are missing, you were probably also missing the original admin account and missing the default settings and permissions right after the installation.
