Option to comment isn't there, please help

HI, For the longest time (years), I have not been able to comment on any YouTube videos I am watching. I am logged in. This happens on either my iPhone or my iMac. I can see the Add comment line, but when I click it and start typing, nothing appears. It's like it is non-functional. I can see comments made by other users but am unable to add my own comments. This happens on all videos I watch so it isn't a case of the owner disabling comments or I have been banned. Do I need to have Premium to comment ? Or, do I need my own Channel to be able to comment on other videos ? I tried to create a channel and that doesn't work either. I have logged out and logged back in to no avail. Any help would be appreciated. Thank you