Unable to convert variable to GMP when initializing Bitpay client class (Laravel)

Question

I have generated my private, public and sin keys according to the documentation, and added their respective paths to my yaml config file.
I can load the main bitpay class fine, however I cannot initialize the client class, as I receive the following error:

PHP warning: gmp_cmp(): Unable to convert variable to GMP - string is not an integer in /home/vagrant/laravel/vendor/bitpay/php-client/src/Bitpay/Math/GmpEngine.php on line 26

What would cause this error?

Answer 1

Bitpay automatically uses the encrypted file store, however the docs suggest that it uses the un-encrypted one by default. Changed it and it works.