From Miraheze Developers Wiki
    Flow\Exception\NoParserException error on a wiki

    When creating or editing a topic using StructuredDiscussions, you may encounter the following error:

    [24 digit hash] Caught exception of type Flow\Exception\NoParserException


    To fix this, follow these steps:

    1. Go to Special:ManageWiki/permissions on the affected wiki.
    2. Select the * group.
    3. Go to "Unassigned Permissions" tab and select writeapi.
    4. Save the page.

    This should fix the issue. If it doesn't, try assigning the writeapi right to the user group.

    See also