Image not displayed in Grayscale mode

Can anyone help me with my media issue?
I’m creating a page for my club and adding media, to the page.
I have no issue with adding a picture that is formatted to RGB, .jpeg and around 60 to 70 Kb. from my media library. But when I try to add picture that is in Grayscale mode, from the media library, of the same size, I get to view all the image settings and the advanced image settings but the image is not displayed on the page.
Here is the freaky thing. If I link to a a separate website where the same Grayscale image is located (not in the Media Library)…It’s displayed with no problem.
What the heck is going on.
Help!!!
Gerry