Проблемы белых айтишников:
https://community.adobe.com/t5/flash-player/ie-11-ignores-allowlisturlpattern-in-mms-cfg/td-p/11426041?page=1

Microsoft will be pushing out an update next month, which will bring that platform into parity with the others.
In the meantime, you can either use the older less-inclusive language, or just wait a couple weeks and your mms.cfg should work as-is.