If you downloaded a free copy of EndNote on to your computer from APU's IT department page: Downloads - Free University Software, then, unfortunately, you eventually will get a notice saying that the license has expired.
At least since Friday, October 20, 2023, the student/faculty free EndNote download for a Mac or PC, is no longer listed. This is because APU chose not to renew their subscription with EndNote. The subscription renewal was due in May 2023. I'm so sorry about any inconvenience.
Either you can pay for the upgrade or work with another Citation Manager software like the free Zotero application.
Here's some information about Zotero: How to Use Zotero.
Also, to see how to transfer your records from your My EndNote Library into Zotero, follow these instructions.
Again, sorry for any inconvenience.