Hello and welcome to the forum, also had this problem and solved like this.
For me this way worked:
Go to settings
Go to general settings
Change Message Editor Interface to another option
Check if you can post vids/pics - if not- check second option - if not
CHANGE IT BACK to the option it was at the beginning
Hope you understand, little strange but after that I could post.
Sorry to hear- if you can change hard or software- that means:
Try computer, tablet, IPad, Phone....
Try a different browser like Chrome, Firefox....
If really nothing works, last chance is to give us your link not as a link and we can copy and paste.