Edited colour mode of uploaded photos changing back to native colour mode in Adobe Portfolio

Hi. Sorry in advance if I don't articulate this properly, still kinda learning my way through things. I've been trying to create a basic portfolio using Adobe Portfolio. One of the photos I want to include was originally taken in colour & then converted to b/w image. Converted image has been saved and uploaded to Adobe portfolio and because it is the first photo in the grid, it appears as the 'profile' pic for that collection of photos. As a 'profile' pic, it is somehow appearing in its original format - full colour, but once you click into the collection itself, the image is in b/w (which is how it should appear). I have no idea what the problem is or how to fix it. Thanks in advance.