Gutenberg Block language translation does not work

only the JS file translation does not work

It’s most likely because WordPress couldn’t find your translation file, which should be in a valid JED format, like so:

{
  "domain": "my-text-domain",
  "locale_data": {
    "my-text-domain": {
      "": {
        "domain":       "my-text-domain",
        "plural-forms": "n != 1",
        "lang":         "en-us"
      },
      "Shortcode Title": [
        "Shortcode Title translated"
      ],
      "Display it?": [
        "Display it? translated"
      ],
      "Another text 1": [
        "Translated text - singular",
        "Translated text - plural"
      ],
      "Another text 2": [
        "Translated text"
        // No plural.
      ]
    }
  }
}

And saved with a name in this format: ${domain}-${locale}-${handle}.json. For example, in your case, it could be my-text-domain-en_US-my-blocks-script.json if the site’s language is English (United States) (see “General Settings” → “Site Language”).

And when you call wp_set_script_translations(), you can specify the third parameter ($path) which is the full absolute file path to the directory containing the JS/JSON translation files. E.g.:

// $pluginurl was taken from your code
wp_set_script_translations( 'my-blocks-script', 'my-text-domain', $pluginurl . '/languages' );

Also, you can use po2json to convert PO/.po files to a JED-compatible JavaScript object or JSON string.

Notes:

• In the above JS/JSON translation data, the locale as in "lang": "{locale}" should be the GlotPress locale as you can see in the table on this page. For example, en-gb for English (UK).

• In your JS/JSON translation file name, the locale as in ${domain}-${locale}-${handle}.json should be the WP locale as you can see in the table on this page. For example, en_GBfor English (UK).