Closed captions not working

Hi, I'm also having problems with getting captions to display. I created an .SRT file separately, then imported into my .story file, using the Import, Captions option, while editing the file in Storyline.

The system definitely knows there is some caption content there (even though nothing is displaying visibly on screen), because if I try and import the caption file a second time, I get a prompt asking whether I want to overwrite the existing captions.

So I can't see the captions themselves when I go to 'Edit captions' from within Storyline - nor do they show up in the Preview - and if I Publish the project, they don't show up there either (I'm publishing in TinCan for LMS).

However, when I preview the video, the 'Caption' icon appears in the video player, which selects on/off (so again, something in Storyline recognises the caption file/content is present) - but nothing appears.

I know this may seem like a very stupid question, but when I originally created the captions (while editing the video in DaVinci Resolve), I formatted the subtitles to be white, on a light grey background. I then exported the video in MP4 format (and inserted in Storyline), with a separate accompanying SRT file. I cannot for the life of me see any way that the SRT file carries over any of the formatting that would have been present in DaVinci - but it struck me that my MP4 video is of software with a predominantly white display - so if white text is showing on a white screen, it would of course be invisible. (But there is no formatting in the SRT file...)

Anyway, I've tried applying a Trigger (as suggested above) to get the captions to appear - but no success.

My Storyline file is HUGE, so not really practical to upload here... any other suggestions, anyone?