Flask Python: Performance Monitoring shows the startup page

Hi…
I am using sentry sdk 0.19.5
and here is how I have setup sentry

import sentry_sdk
from sentry_sdk.integrations.flask import FlaskIntegration


sentry_sdk.init(
    dsn=SentryIntegrationDSN.dsn,
    integrations=[FlaskIntegration()],
    traces_sample_rate=1.0
)

But the performance tab is not showing anything.
How to fix this?