YouTube Live Chat can take up to 24 hours to appear on your YouTube Live videos. As long as your video is public when you stream it and you have Live Chat enabled on your channel, live comments will show up after YouTube has processed the video.
It could also be that for some reason the Live Chat Replay is turned off for your channel. Here's how to turn it back on for future streams:
- Head over to your YouTube Live Dashboard.
- Click Edit in the top right.
- Click Customization, check Live chat replay, then click SAVE.
Now your broadcasts going forward should have the live chat replay available when re-watching your livestream!