I use google photos. When I want to post pictures from photos nothing shows up. In google photo's I will right click the photo, click share, get the link address for the photo, then click on insert photo on the advanced post tab. I then paste the url I copied from google photos, the proper coding seems to appear in the draft with the img wrapped in parentheses followed by the url and the img again. So everything looks proper in the draft, but nothing show up when the post is posted. I know this is kind of convoluted but I hope it makes sense. The only way to insert images is to download them to the computer, and post them as an attachment.
Some sites will block direct linked photos because it uses up their bandwidth to display them on this forum.