Saw this on another site:
1. Make sure you logged out from Amex in a mobile browser.
2. Open google.com and search for “american express business card”.
3. DO NOT open Ad link. (it contains 25K offer only)
4. Scroll down until you see “Small Business Cards – American…” in the search results and click it.
5. Go inside and hopefully you will see 75K offer for Gold and 75K for Platinum.
Although it says only on a mobile browser, I did not get the offer on my phone. I then tried it on my desktop and I got it!