. I’m facing an issue after upgrading from Dash 2.8.1 to 2.17.2.
When I navigate from another page to the default page (via dcc.Location or dcc.Link), the layout loads correctly, but no data is rendered. I noticed that the first long callback — which stores a DataFrame in a dcc.Store — returns a 204 No Content response on initial navigation. However, if I refresh the same page, the data loads properly and everything works as expected.
This same code works perfectly in my local environment and on another server running Dash 2.8.1. The issue only appears in the environment running Dash 2.17.2.
Key points:
• The long callback is triggered when the page path matches.
• It stores data in a dcc.Store.
• The callback works fine on refresh, but not on first-time navigation to the page.
• No errors are shown — just a 204 response from the callback.
Has anyone else experienced this behavior with long callbacks in newer versions of Dash? Could this be related to layout hydration or component mounting timing?
Any insights or suggestions would be appreciated