ecart PayPal checkout failure

While updating site from mysql to mysqli I've lost eCart functionality. The checkout process works fine until I get to PayPal. I can login on the PayPal Express form but when I submit the order all I get is a blank, white page. If I use the old pp_confirm page instead of the newer version, PayPal stalls at the same place but is able to send me back to the checkout_failure page on my site; however, I'm not able to get beyond this step in the Paypal order process with either the old or the updated pages. The old pages worked during June (the last time we needed to use them).

I don't know what I am doing wrong or what I need to do to correct the situation. I've enclosed a set of the old checkout pages and a set of the updated pages if that helps. Nothing stands out between the sets of pages that looks "off" to me. I checked all the credentials on the PayPal site and they are all correct. I tried to ensure the .htaccess file accepts either www. or not, but I don't know if I did that correctly or just made things worse. Also, my webhost recently moved the site (without telling me) to a different server with php7 so I don't know if something changed when that happened that is affecting the process. I haven't been able to register anyone for classes so far this month which isn't good. Would you please help me get this running again? Thanks!