Automatic opening of Illustrator files from within PDF now broken in latest version

Hello, apologies if this has been covered already but I have searched unsuccessfully for an answer.

My problem is this. I use a PDF here at work that when a user clicks a button, it opens an associated Illustrator file. I get this pop up, but it works fine. I am using version 2019.010.20099 of Acrobat Pro DC.

My colleagues, however, have been updated to a later version: 2019.012.20040

When they click on the button, they get the same pop-up but Adobe Illustrator CC 2018 has changed to Adobe Illustrator.app and the feature no longer works as Acrobat is not making the correct connection with Illustrator and just says 'application not found' or words to that effect. Is this a known issue? Is there a workaround?

Thanks

JTH