The ota webpage didn't work properly in Internet Explorer 11, when clicking the "start upgrade" button it returned an invalid state error.
This can be fixed inside "ota_server_web_page.c" by moving:
" xhr.timeout = 2000;\r\n" \
" xhr.open('POST', upgrade_chunk_url_with_query , true);\r\n" \
IE apparently doesn't allow to set the timeout before the connection is opened.
Thank you for the find! We'll check it out and update it on the next SDK.