Call to undefined function mailchimp_apikey_ready_access()

I'm getting a fatal error after updating to 7.5: "Error: Call to undefined function mailchimp_apikey_ready_access() in
/var/www/vhosts/fxpfitness.com/sites/all/modules/mailchimp/modules/mailchimp_activity/mailchimp_activity.module,
line 53"

I've marked as critical as the site is WSODing on this error.
This is a support issue now. I have to figure out how to manually update the module.