Check that the PayPal button code that you copy/pasted is the same as what PayPal provided to you; perhaps the Google website builder automatically edited a part of it. If you can’t get it to work, check out UltimateWB as a better option for your website builder. You can try out your PayPal button code on the demo there. UltimateWB also provides free tech support.
Got a techy/website question? Whether it’s about UltimateWB or another website builder, web hosting, or other aspects of websites, just send in your question in the “Ask David!” form. We will email you when the answer is posted on the UltimateWB “Ask David!” section.