I have tested your code in a Magento2.2 installation and it works

I assume you have a well registered working module named vendor_module

So I suspect maybe there is a typo when you say vendor\module, are your folders really lowercase?

If there are no typo error, have you run both bin/magento setup:upgrade & bin/magento setup:di:compile commands?

If we've reached here, then the only explanation is you have some 3rd party extension installed, which is causing customer_register_success event not to be fired

I have tested your code in a Magento2.2 installation and it works

I assume you have a well registered working module named vendor_module

So I suspect maybe there is a typo when you say vendor\module, are your module name & folders really lowercase?

If there are no typo error, have you run both bin/magento setup:upgrade & bin/magento setup:di:compile commands?

If we've reached here, then the only explanation is you have some 3rd party extension installed, which is causing customer_register_success event not to be fired

I have tested your code in a Magento2.2 installation and it works

So I suspect maybe there is a typo when you say vendor\module, are your folders really lowercase?

If there are no typo error, have you run both bin/magento setup:upgrade & bin/magento setup:di:compile commands?

If we've reached here, then the only explanation is you have some 3rd party extension installed, which is causing customer_register_success event not to be fired

I have tested your code in a Magento2.2 installation and it works

I assume you have a well registered working module named vendor_module

So I suspect maybe there is a typo when you say vendor\module, are your folders really lowercase?

If there are no typo error, have you run both bin/magento setup:upgrade & bin/magento setup:di:compile commands?

If we've reached here, then the only explanation is you have some 3rd party extension installed, which is causing customer_register_success event not to be fired