Getting Error applying discount code [1]

HI

I am getting a Error applying discount code [1], when using discount codes.
I check all the setting and I guess it is fine.
I checked the console and it has a error:

GET https://***.com/wp-admin/?action=applydiscountcode&code=test&level=1&msgfield=pmpro_message
404 Not Found 4.01s

What can be the issue?

Thanks