cannot post photos on any part of facebook

this problem starte a few days ago.
when trying to figure out what might have changed, i realized i had changed firefox to 64 bit.
however, the problem also occurs on chrome.
i cannot post photos to my timeline, friends' timelines, in comments or in messages.
see screenshots.
any advice??
thanks!!!

Have you tried to reinstall any of the browsers, also try resetting Internet Options to default in Control Panel and clearing Internet Data.

hi, anonjwm. thanks for the reply.
i've already done that.
i just discovered that (of course) there is no problem on edge.
the ony problem is i don't want to use edge.
i was thinking that this problem might have been the result of one of the 4/12 updates, so i tried to uninstall the only one that might have anything to do with this--the 'cumulative update for windows 10, but when i tried to uninstall it, after several minutes, a popup came up saying that 'some of the updates could not be uninstalled'.
wonder if this has something to do with it...
note: i have just reinstalled firefox and there is no change.
thank you!