Storyline 2 files displaying as HTML5, not intended to
I have recently developed some modules on Storyline 2. They are published as flash and uploaded to our client's LMS. However, for a few users, the modules play as HTML5 and the user gets stuck at certain screens that won't progress. For the majority of users there is no issue as the modules play in flash. I presume the issue is with the users browser or some other settings on their computer which is playing the html5 file.
Does anyone know what the settings may be that are making them bypass the flash file?
Any help greatly appreciated!