When I try to pay with Mastercard credit card module I get an error
bad request 400
If I go to my
var/log/exception.log file I receive the following error:
main.CRITICAL: The HOME or COMPOSER_HOME environment variable must be set for composer to run correctly at /var/www/html/emall/vendor/composer/composer/src/Composer/Factory.php:641)"} 
I have tried many commands found in Internet, but I don´t know if the problem is with composer or with the module itself. This is the module that im using: https://marketplace.magento.com/ontap-module-mastercard.html
Hope someone can help. Thank you and regards!