@anricat &
@disneycruisedreams
OK, this is what I did and it did FINALLY work.
* I got around the "We can't apply this code to your order" error by selecting PayPal as payment and entering the eBay GC codes in the SECOND screen.
* The GCs were accepted and then it said $0.00 to PayPal, and a blue "Continue" button.
* I clicked on the Continue button and logged into PayPal and received the "At this time, we are unable to process your request. Please return to eBay and try another option." message.
* I thought, what the heck? maybe I needed a non GC item in my checkout so I added another PPDG card to the checkout and a Speedo nose clip. I had bought $23 worth of swimming nose clips yesterday with a $25 GC with no problem. So, I had $201.68 in gift cards and another approx $4 in PayPal. I got the same message

. So, adding on non gift card item did not work.
* Along the way I had to have the PayPal automated system call my home phone twice and I had to change my password once.
* I finally called PayPal and got a super sweet associate on the phone. It took her only about 10 minutes to fix things. She had to go through a high level verification process where they had to ask me questions that only I would know (things like streets where I once lived). Once I passed (with flying colors, LOL) I was able to click on the blue Continue button and the order went through! I have another nose clip (6 now, including the 5 I purchased yesterday) but those won't last the season so I'm OK adding it as an experiment.
The next time this happens to me I'll just call and tell them that the high level verification questions worked.