Error with Jira misc custom fields

[Michael]

I have screens with custom fields that are no longer populating for new or older issues and instead are throwing the following error: 

Error:

You don't have a Jira Misc Custom Fields app license

This had worked previously and now has randomly stopped, any ideas? 

Thanks.

[David Fischer]

Did you upgrade JMCF to version 2.x? The upgrade button mentioned "Paid upgrade", which means that you need to purchase a license. See the "Manage apps" (or "Manage add-ons") admin page within your Jira instance.