Erro ao gerar bootstrap

Boa noite, está ocorrendo erro ao subir o servidor:

[1] [Browsersync] Watching files...
[1] 19.03.19 21:15:49 304 GET /index.html
[1] 19.03.19 21:15:49 304 GET /css/bootstrap.css
[1] 19.03.19 21:15:49 304 GET /css/bootstrap-theme.css
[1] 19.03.19 21:15:49 304 GET /lib/jquery.min.js
[1] 19.03.19 21:15:49 304 GET /lib/system.js
[1] 19.03.19 21:15:49 304 GET /js/app.js
[1] 19.03.19 21:15:52 304 GET /css/bootstrap.css
[1] 19.03.19 21:15:52 304 GET /css/bootstrap-theme.css
[1] 19.03.19 21:15:53 304 GET /lib/system.js.map
[1] 19.03.19 21:15:53 404 GET /css/bootstrap.css.map
[1] 19.03.19 21:15:53 404 GET /css/bootstrap-theme.css.map

E no navegador aparece esse erro:

(index):48 (SystemJS) NegociacaoController is not defined
    ReferenceError: NegociacaoController is not defined
        at eval (http://localhost:3000/js/app.js:1:20)
        at eval (<anonymous>)
    Evaluating http://localhost:3000/js/app.js
    Error loading http://localhost:3000/js/app.js

Sabe o que pode ser?