Download links stopped working completely

Hi there – I have two web sites which use download manager.

Both have wordpress 5.4.2 installed with download manager plugin installed and running.

Downloads work on one and have stopped working on the other.

In one of the installations the download manager settings area includes the “image button” feature.

When I select and save “no image”, the button image remains the same as before.

Is this connected to the fact that downloads no longer work?

NB I have tried deactivating and removing download manager and then reinstalling it but that has not restored the download function.