求助！RFE Beneficiary Qualification need license/certification

Hi, H1b transfer 不幸被RFE(Beneficiary Qualification)。大体意思就是我没有证明该职位/专业（本人mechanical engineer）不需要license/certification，声称handbook上说“Mechanical engineers typically need a bachelor’s degree in mechanical engineering or mechanical engineering technology. All states and the District of Columbia require mechanical engineers who sell services to the public to be licensed.“很难找到律师建议的官方statement说我这个职位/专业不需要license/certification。请问大家有没有高见该如何准备材料，感谢！！