Your experience has not been accepted because the name of the signatory is not mentioned on the letter

Hi,
I have applied for ACS Skill Assessment and got a negative result with following summary,

  1. Your Bachelor degree has been accepted as equivalent to AQF Bachelor which is major in ICT.
  2. My first work (3 years and 7months) experience has been accepted as closely related to nominated ANZSCO.
  3. My second experience (9 years) has not been accepted because the name of the
    signatory is not mentioned on the letter. (Please note that my experience letter was digitally signed and only the title of signatory was mentioned)

Please advise what should be the next step as I was already in review.

Regards,