The new process to redeem karma credits - in effect since May 2017 - is described here: https://jmir.zendesk.com/hc/en-us/articles/115000200912
If this fails, please send an email to firstname.lastname@example.org stating how many Karma Credits you would like to redeem, and for what purpose (e.g. apply to the Article Processing Fee). Your request will be processed by a tech support agent shortly after.
*WARNING*: Requests to redeem karma must be made prior to making payment to the item you wish to apply the karma to (eg: Submission fee, Article Processing Fee, etc.). If you request karma please wait for a JMIR tech to respond with a message before making payment.