average_human

Make sure to have the item you want to inpaint and the background (what you want the new thing to be) on the same layer, or "Flat" OR select both of the layers. It works!!!

I have had the same issue!! I make sure the picture is selected, but as soon as I click on the inpainting tool, The image deselects. It is only in ONE window in the Affinity Photo program. I had used the tool earlier today, and it worked fine. I can use the tool on all other documents, just not the one I need to change. This has happened before, and usually it works after an hour or so.... but it is still annoying!