Assignee Export Showing Null For Updated Users

Using the format below, we are getting empty cells in an Excel export for Assignees whose username values have been modified:

${link:title=${fullname:AssigneeId}, href=$\ Unknown macro: {emailaddress} }

The error that appears in the logs is:

2017-10-05 11:35:14,892 http-nio-8013-exec-90 WARN username xxxxx xxxxx x.x.x.x, x.x.x.x /sr/com.xpandit.plugins.jiraxporter:xporter-currentfield-xlsx/temp/SearchRequest.xlsx [c.x.j.c.d.b.a.mapping.processor.FullNameMappingProcessor] Unrecognized user: user789@domain.com

Recently we changed our username standard in our JIRA system.  Originally a user may have logged in with "user789@domain.com" but now they log in with "user789" or something different depending on their requirements.  With this change, these users are not showing up in the Assignee column of any export, while users who did not have their username updated are displaying correctly.

The built-in "XLSX (Current Fields)" export also results in the same error for Assignee values.  I have reindexed JIRA but that did not solve the issue.