500 Error after move to new host

I’m in the process of moving our sites to a new host and have run into a problem with this PayPal plugin.

Adding a product to cart and attempting to checkout, when I click on the PayPal button, the popup window displays briefly, but then closes immediately. Console shows a 500 error for this url: https://flow-rite.tempurl.host/wc-api/PPCP_Paypal_Checkout_For_Woocommerce_Button_Manager/?ppcp_action=create_order&utm_nooverride=1&from=checkout

Followed by a json error, but that is only because the error from above is a web page, not a json response.

I’ve tried to compare settings between old and new site, as far as I can tell, all settings match. Any suggestions where else to look?

The page I need help with: [log in to see the link]