Sometimes due to system-wide energy saving rules, the Apple Watch can take some time to sync data. If you see an arrow sign, the workouts are downloading, but they need time. It may help to put the Apple Watch on your charger and leave it running in the foreground on both the iPhone and watch.
The most important thing is to give the watch screen time. Do this by scrolling on the crown every few minutes to keep the screen on. Every once in awhile, be sure to open and close both apps (i.e. hit the home button/crown, and then open the app again).
Another way to encourage your workouts to download fully is to run other workouts on the Apple watch while you're waiting.
If your workouts are still refusing to download, make sure you are signed in to your Seven account in the Profile section. Then, uninstall the app from your iPhone, re-download it from App Store and sign back in. Wait for a few minutes with your Apple Watch app in the foreground to sync downloads etc.