Unable to uninstall Slack from the App Store

One of my colleagues is unable to uninstall Slack from the app store. It's tied to a company Apple ID we no longer use. The user also has the latest version of Slack installed from their website.

Is it worth un-installing any versions of Slack and starting from scratch?

He's only having this issue with Slack (with the company Apple ID), he's been able to remove various other apps.

Any suggestions will be much appreciated.

Thanks.

Rob