Hi Tim,
If you saw my initial post, please ignore.
In this case, the Matrix documentation for the PayPal gateway is a little out-of-date, if you have version 5.1 (or 5.0.1.2) or newer - for instance, you may notice that there’s no need to enter the path to PPCrypto.php in the PayPal Configuration asset anymore.
According to Squizmap #5394, the function provided by PPCrypto was merged into Matrix’s PayPal Button asset in version 5.1, so you no longer need the old PPCrypto.php file anymore.
Hope this helps.