The answer you have been seeking is:
1. Log in to your american express account at americanexpress.com
2. Hover your mouse over the "Benefits" drop down menu in "Account Home" then click "Card Benefits"
3. A screen will now load which will allow you to choose between all your Amex Products, click on the image of the BCP
4. On the "Distinct Benefits and Services" screen click the "See all benefits" tab
5. On the next screen under the "Cash Rewards" drop down menu you will find your hard worked for "Refer A Friend and You can get $75" option.
6. Click on that option and then the "Refer a friend link" which is loaded in that frame
Starting Score: 770
@steve23111 wrote:
@CreditMuppet wrote:The answer you have been seeking is:
1. Log in to your american express account at americanexpress.com
2. Hover your mouse over the "Benefits" drop down menu in "Account Home" then click "Card Benefits"
3. A screen will now load which will allow you to choose between all your Amex Products, click on the image of the BCP
4. On the "Distinct Benefits and Services" screen click the "See all benefits" tab
5. On the next screen under the "Cash Rewards" drop down menu you will find your hard worked for "Refer A Friend and You can get $75" option.
6. Click on that option and then the "Refer a friend link" which is loaded in that frame
Good up until step 3. Takes me straight to the benefits of my Clear card. There is a dropdown box in the top right corner that says "Find Another Card" however Blue Cash Preferred is not listed, and is probably the only current card that does not make an appearance in that list. BCE is there, as is the regular BC card. There are no card images shown.
On step 3 there should be a mini image of your other card(s) on the top left next to the picture of your clear card (in my case the PR gold). In my case next to the picture of my Premier Rewards Gold card, there is a small image of my Blue Cash Preferred, which when clicked will load the benefits for that card, I`m not referring to that drop down you mention, look <-------------- and down a little
Of course depending on what products you have the page could be built differently given these are dynamic websites.
I'm sure that's how it *should* work, but that's not how it *is* working. 
@steve23111 wrote:I'm sure that's how it *should* work, but that's not how it *is* working.
Works everytime for me, you will need to make sure all your products are under the same account for my instructions to work (one login)
There are other links to this refer a friend program (ie via "blue rewards program" under the rewards summary page) but those other links, although not very clear are actually for OPEN business cardmembers and look to be incorrectly linked to me, in that case you will get an error stating that your account is not eligable.
@steve23111 wrote:I'm sure that's how it *should* work, but that's not how it *is* working.
Try also going in to your browser settings, clear your browser cookies, close the browser and try again. The AMEX site is nortorious for relying on cookies!
Edit: Dont use the 'search for refer' method for doing this, it will take you to the refer a friend version for OPEN business cardmembers and hence the 'not eligable' error
As a further update, sometime today a "Refer a Friend" link appeared on the left-hand side of the "View All Personal Cards" page while logged in to the AMEX web site. When clicking this, it does give me the option of referring either Zync or Blue Cash Preferred. Interestingly, if I click the "Refer Friends and Earn Rewards" link just above it and to the right, the only option I have is Zync. Oh well, it's a start!