I was having the same issue after upgrading PHP on my VPS, and @hmeatball ‘s solution worked initially, but then as I activated other plugins, WordPress would crash again.
What ended up working for me was turning on wp debug mode in wp-config, which triggered WordPress to display a message on my site that the memory allotment had been exceeded. Turns out PHP upgrades reset PHP settings in cPanel. I increased the PHP limit and boom, all my WordPress websites affected by this issue were displaying flawlessly again and I just reset all plugin setups in phpMyAdmin.
Also received an order that used the same information. Googled it and found this post.
I disabled the “PayPal Checkout” payment option and have gone through “PayPal Standard” instead. Not sure if that will help.
Also, I use the “Sucuri Security – Auditing, Malware Scanner and Hardening” plugin, and realized I had not requested an API key, which I now did. Just make sure to turn off alerts for super mundane stuff.
