Upload fail

Hi, I've been trying to upload a bunch of jpg pictures and I get the same fail error message all the time :
XHR returned response code 403,
please advise ?

Hello Sabine!

The response code 403 means that you are not allowed to upload here. You may logged out in another tab? If the problem still persists when you are logged in please send me the admin link to support@pollunit.com

Best regards
Markus