It sounds like you’re using Strava to sync data to Intervals. This comes up a lot, read a few posts up about it. Short version: Strava changed their policies and any data synced to intervals.icu cannot be shared via their data api. You won’t see that data in any of the Intervals apps that have been built. Use direct connections to intervals from Garmin, Wahoo, Zwift, etc instead, or use an app like RunGap or HealthFit (for Apple activities) to sync data. You can’t use Strava as your data hub anymore, they own everything you send there regardless if you recorded it with their software or something else. I have a big gap in my history now because of it too.
I recommend everyone let Strava know how they feel about this. I personally chose to stop my 10+ year subscription over it. Data ownership and openness is one of the many reasons I like Intervals.