Adobe Flash was made End of Life (EOL) at the end of December 2020 but Adobe gave users a short period of grace until turning the product off on 12 January 2021. As of today any websites will no longer be able to play Adobe Flash content as it is blocked by Adobe.
However there is a way to still run Flash applications if you have access to Internet Explorer 11 and haven't applied the patch to remove Flash (KB4577586) We have successfully used this method to reactivate one of our applications that relied on Flash based graphs and had stopped working on Jan 12 but users are now able to access again. Bear in mind this should only be a temporary fix until you can rewrite the code, using Flash is not a long term solution. You need to create a file called MMS.cfg. Within the file you need to specify the domain and port that your flash application is running on, for example https://https://www.bbc.co.uk/:80. This is the website/domain for your website that you need to enable flash to work on.