Have you opened a case with Certification Support? They would be who I would talk to first to try and resolve this.
They typically ask you to verify your mailing address after you pass your exam, was your new address reflected at that time?
You can always pay a few extra $$ and get the electronic certificate which can then be printed out on heavier stock paper. What they send you these days is nothing stellar, but they do send out a neat sheath to keep it in.
Regardless, congratulations on passing!
First of all, congratulations on passing your CCNA exam!
Please note that upon becoming certified, candidate's receive a congratulatory email with specific instructions to confirm or update their Preferred Mailing Address in their Certification Tracking System profile. These instructions will ensure that candidates choose their preferred kit type and that their certificate kit is shipped to the correct location.
Hard copy certificates can take 6-8 weeks for delivery (via US Postal Service) after it has been shipped while soft copy kits can take up to 10 business days.
Since it has been more than 8 weeks, you may contact the Certification & Communities Support team once again to inquire about your certificate OR you have the option to purchase an additional kit.
For purchasing instructions, please click here.
Hope this helps.
Cisco Learning Network Moderator