"UserImportExportPlugin was not found on this server."

Describe the issue or problem
We are changing our journal’s title and have created a “new” journal in OJS to facilitate this. I am attempting to import the users from our “old” journal to the new one, but I receive the following error when I try to use the “Users XML Plugin” under the Import/Export tools tab:

The requested URL /index.php/[Name of journal]/management/importexport/plugin/UserImportExportPlugin was not found on this server.

I also receive the same error when trying to use the
“[Native XML Plugin] Import and export articles and issues in OJS’s native XML format.” option.

Steps I took leading up to the issue
I receive this error on both the “old” and “new” journals within OJS.

What application are you using?
OJS 3.1.2.1

Additional information
Please add any screenshots, logs or other information we can use to investigate this problem.

Hello @RWA,

Please note that the version of OJS that you’re using is no longer supported by PKP. I highly recommend that you upgrade to the newest version of OJS, as it is possible that your issue will be resolved by upgrading. However, other community members may wish to offer assistance.

Upgrading instructions are available in the PKP Administrator’s Guide and as part of our [Upgrade Guide] (https://docs.pkp.sfu.ca/dev/upgrade-guide/).

Information about the latest version of OJS can be found on the PKP Website

-Roger
PKP Team