Gulp - BrowserSync says "cant get /", how to solve the problem?

Question

gulp.js

I have a gulpfile that handles css and livereload:

const gulp         = require('gulp'),
    browserSync  = require('browser-sync'),
    concat       = require('gulp-concat'),
    cleanCSS     = require('gulp-clean-css'),
    del          = require('del'),
    autoprefixer = require('gulp-autoprefixer');

gulp.task('styles', function() {
  return gulp.src('./css/*.css')
    .pipe(concat('style.css'))
    .pipe(autoprefixer())
    .pipe(cleanCss({
      level: 2
    }))
    .pipe(gulp.dest('./dist/css'))
});

gulp.task('clean', async function() {
  return del.sync('./dist/css/*');
});

gulp.task('browser-sync', function() {
    browserSync({
        server: { 
            baseDir: './'
        },
        notify: false
    });
});

gulp.task('watch', gulp.series('browser-sync'), function() {
    gulp.watch("./css/*.css", browserSync.reload);
    gulp.watch("./html/*.html", browserSync.reload);
});

gulp.task('default', gulp.series('watch'));
gulp.task('build', gulp.parallel('clean', 'styles'));

The build works well, but the live reload stubbornly refuses to work: If you enter the project folder, then "CANT GET /" is displayed on the page, and if you enter a folder with html files, it updates only html and does not include styles

at all. What could be the problem?