Gulp - Can't run tasks sequentially. How to do it in Gulp 4?

Question

Node.js

My task: 1. Compile
SCSS to the build/ folder 2.
Copy the resulting css to the test folder . By the gulp build command, build/style.css is created, but not copied to test . If you run gulp copy:css separately, it is copied. Task code:

gulp.task('build', gulp.series(
  'clean',
  'css',
  'copy:css',
));

// gulp clean - очистка build
gulp.task('clean', (done) => {
  del( config.dest.root ); 
  done();
});

gulp.task('css', (done) => {
    gulp.src( config.src.cssEntry )
        .pipe(sass({outputStyle: 'expanded'} )
        .pipe(concat('style.css'))
        .pipe(gulp.dest( config.dest.css ) );
    done();
});

gulp.task('copy:css', (done) => {
    gulp.src('build/css/**/*.*').pipe(gulp.dest('test/css/'));
    done();
});

UPD: If you set the exact path to style.css

gulp.task('copy:css', (done) => {
    gulp.src('build/css/style.css').pipe(gulp.dest('test/css/'));
    // gulp.src('build/**/*.css').pipe(gulp.dest('test/'));
    done();
});

Gives an error message

[09:42:34] Starting 'css'...
[09:42:34] Finished 'css' after 11 ms
[09:42:34] Starting 'copy-wp:css'...
tree
[09:42:34] Finished 'copy-wp:css' after 6.87 ms
[09:42:34] Finished 'default' after 33 ms
events.js:183
      throw er; // Unhandled 'error' event
      ^

Error: File not found with singular glob: D:/!!!DB_TopTools/OpenServer/domains/debug-gulp-wp/wp-content/themes/build/css/style.css (if this was purposeful, use `allowEmpty` option)
    at Glob.<anonymous> (D:\!!!DB_TopTools\OpenServer\domains\debug-gulp-wp\wp-content\themes\node_modules\gulp\node_modules\glob-stream\readable.js:84:17)
    at Object.onceWrapper (events.js:315:30)