Depending on what you're trying to do, this could mean a couple of different things:
If you're just looking for general tips, you can find helpful subtitling do's and don'ts from or troubleshooting steps from Crunchyroll for web playback issues. Subtitling tips: Do's and don'ts - LanguageWire subtitle Instant.Dreams.2017.WEBRip.x264-ION10I...
:srt or .ass subtitle file that matches that specific video release ( WEBRip.x264-ION10 )? Troubleshooting & Setup : Depending on what you're trying to do, this