Hi
It may help to follow the app developer's troubleshooting steps:
- https://help.instagram.com/370569449686414
- https://help.instagram.com/489243821222605?helpref=breadcrumb
If reinstalling the app, it may help to follow these steps:
- Remove Instagram from your Apple Watch:
On your iPhone, in the Watch app, go to: My Watch (tab) > scroll down to the list of apps > tap on Instagram > turn off Show App on Apple Watch (allow a short time for the app to be removed).
- Remove Instagram from your iPhone:
Touch and gently hold your finger on the Instagram app icon until the icon jiggles > tap the "X" next to the icon to remove the app > press the Home button.
- On your iPhone, reinstall Instagram from the App Store (which will also ensure that you are using the latest version).
- Reinstall the app on your watch
Via My Watch > Instagram > turn on Show App on Apple Watch and waiting until the process completes.
- Open the app on your iPhone and sign in.
- Open the app on your watch.
If the issue persists, then I suggest that you contact Instagram for assistance: