Can't pm

I’m trying to pm a user but when I hit “send” nothing happens, what should I do?

Edit: I get this error when I add an image, I didn’t add anything else apart from the image :
The following errors occurred with your submission

  • The text that you have entered is too long (410193 characters). Please shorten it to 5000 characters long.

How large was the image (in kilobytes or megabytes)? Also what image format is the image saved in?

it’s a jpeg and the size is 300ko

And I should’ve asked this at the start, but could you tell me your operating system and the web browser that you’re using. Also, are you using any extensions in that browser?