Javascript upto date/on?
The three dots at the top, assuming you're using a tablet/phone. Settings, from there go to site settings and scroll to Content. You'll see if javascript is active thereI wouldn't know how to check but I'd assume so as the other site's working alright.
This won't help but your not alone. I can post photos at present but I do get the same problem you describe from time to time.It's only started happening today but, I press attach file to add a photo to my post, the box turns blue as if something'happening, but it doesn't go any further.
I've had a mooch in my profile settings to see if anything is disabled but can't find anything.
Your way works for me (above), but I usually just find the image I want then ctrl-c, ctrl-v.What I usually do when I want to post a photo is press the attach files button below the dialogue box, this then lets me open my phone gallery and pick a photo, I then press the insert box that's overlaying the photo to insert it either as a full image or smaller attachment style.