Hi @RickMath,
The REVIEW_REMIND email template should be present in new OJS 3.1.0-1 installs, and the upgrade process should’ve taken care of adapting any changed email variables from the 2.4.x versions of your templates. I’m not sure what happened in this case. You can find the text of the English-language templates for OJS 3.1.0-1 here.
Regards,
Alec Smecher
Public Knowledge Project Team