After you click the Share button, the "Uploading" dialog box appears, but it never closes.

Such an error message one can see in console:

"Access to XMLHttpRequest at 'http://www.openscreenshot.com/upload3.asp' from origin 'chrome-extension://akgpcdalpfphjmfifkmfbpdmgdmeeaeo' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource."