Sounds like your "image path" has only the name of the file instead of the complete file path to your image file.
Define a calculation field set to return text and just enter your container field's name as the "calculation".
Place this field on your layout and make it several lines of text tall so you can see all the lines of text in it. Examine this text for possible errors in your file path.
You can even use Insert Picture to insert a picture into your container field and then check this calculation field to get the correct format for an imported picture. (You'll only need the last part that starts with "imagewin" or "imagemac".)
Just dropping a line to say that I found this post very useful! Thanks @PhilModJunk :-)
If I have no idea on how to write a FM calculation and want to achive this path to container?
What is the formula