Hi - I was running into this same problem and wanted to check out my solution before posting to anybody here. There is a way to do it, but it took me a few steps to get mine to work. Here's what I did.
I both buy and sell on ebay as a hobby only. I'm verified with PayPal and so I have a bank account and credit card linked to my PayPal account. I prefer to pay for purchases with my linked credit card...NOT with PayPal funds or going into my bank account. Whenever I sell something I usually transfer the money pretty quickly out of PayPal and into my bank account, so I usually have a $0 balance in Paypal. I recently sold some things and wanted to buy something about the same time. When I went to pay for my item, my credit card would not come up as a payment option...only my PayPal funds or my bank account. I thought maybe my credit card (which I had recently updated) had gotten deleted, but when I went in to "my account" "edit/add a credit card" it showed it was already there. That's when I realized what my problem was...I had money sitting in my PayPal account...enough money to pay for my purchase. PayPal's algorithm says it will always pull from any funds sitting in the PayPal account first, and if no funds are there it will go to what you have designated as your primary account next. Somehow my bank account had gotten changed to my primary account instead of the way I wanted it, which was for primary to be the credit card. So first I checked in "my account" and into the "edit credit/debit card" and found that small little button on that "edit" page near the top that says "make this my primary (optional)" and I checked it and saved it. Then I transferred my funds out of PayPal so that I had a zero balance. Then I went in to pay for my purchase and found that now my bank account AND my credit card were showing up as choices for Payment just like I wanted with my credit card also designated as my backup funds account. Now I was able to choose the credit card for my payment source.
So the secret to being able to use your credit card for payments rather than your bank account is make sure you go into that edit page for your credit card and check that little "make primary" box and then make sure you don't have enough funds in your PayPal account to pay for what you are buying and your credit card should come up as a payment option, Not sure exactly how that would work with a debit card, since most debit cards are linked back to your bank account (unless you have more than one bank account linked to your PayPal and then force the separate account linked with your debit card to be your primary by checking that little "make this account primary (optional )" on the edit page., but I know this will work for forcing it to let you use your credit card, cuz I just got it to work.
