This is pretty strange. The Invig never asks for Illustrator files, it only asks for missing maps used by materils or object styles.
1- Is it possible that you opened the .ai file in Photoshop and then saved it as a .tga or .jpg or .pct file but left it’s name the same?
2- Do a search on your computer for this name and see if it appears more than once. The fact that the file is dimmed when you navigate to it shows that that really isn’t the file it is asking for. It may have the same name, but it’s not the correct file type.
3- Are you restarting with a “template project” each time? Does this problem happen when you create a completely new project from scratch?
4- If it is asking for a map there is a material or object style in this project that uses that map. The material or object style doesn’t have to be applied to an object to get this message. At some point in the past you have saved a material or object style to the bins and then moved the map that it needed. To fix it you need to figure out which material or object style wants this map and then delete it from the bin.
Best,
Zax