Animation Render Baker - Not sure how to save file


I’m trying to use the Animation Render Baker add-on to bake the lighting information of an object to an image sequence.
However following the manual, I’m unsure how to save the texture before baking.

  • Normal baking a single file works perfectly. But the add-on seems to complain about it not being saved first. Though I believe I certainly have through - Image > Save Image As > Filename

Attached an image showing the popup error.

Help would be really appreciated,