Why PEG parser can't parse simple Markdown?

Question

This grammar

block      = ph+ space* end
ph         = space* ph_line+
ph_line    = (~"\\n\\n" any)+ "\\n"

can't parse this text

const text = `
# Title

some
`

Error

error: Can't parse block: Line 5, col 1:
  4 | some
> 5 | 
      ^
Expected "\n"
      at parse_block (/Users/alex/base/projects/ts/play.js:30:33)
      at /Users/alex/base/projects/ts/play.js:34:11

Full code

const ohm = require('ohm-js')

const block_grammar = ohm.grammar(`
  Markdown {
    block      = ph+ space* end
    ph         = space* ph_line+
    ph_line    = (~"\\n\\n" any)+ "\\n"
  }
`)

const block_semantics = block_grammar.createSemantics().addOperation('parse_block', {
  block(items, _space, _postfix) {
    return {
      items: items.children.map((c) => c.parse_block()),
      tags:  tags.children.map((c) => c.parse_block())
  } },

  ph(_space, lines) { return {
    type:  'ph',
    lines: lines.children.map((it) => it.parse_block())
  } },
  ph_line(text, _postfix) { return text.sourceString },

  _terminal() { return this.sourceString },
})

export function parse_block(text) {
  text = "\n" + text.trim() + "\n"
  const match = block_grammar.match(text)
  if (!match.succeeded()) throw new Error(`Can't parse block: ${match.message}`);
  return block_semantics(match).blocks()
}

const b = parse_block(`
# Title

some
`)

console.log(b)