It happened right a way for me.
You may want to call PayPal for tech support.
I called them twice last Friday. I'm offering consulting via phone on my site. since it isn't "physical" I can't use e junkie. I could not for the life of me get the pay page to open. I kept getting an error. One tech directed me to this "test bed." I didn't know what that that was.
Just delete what's in there, past in your code, click display. If the code is correct, it'll show up.
My code was correct, but I still couldn't get it to work.
Another tip from the tech is make sure the code is pasting in exactly.
So, I ended up installing WP Nice PayPal Button Lite plugin and it works perfectly. If you have a WordPress site, check the plugins.
I'm sure you'll find a way through all the frustration.