This issue is caused by database/metadata incompatibility after a major version upgrade, not by a browser or theme problem.
The earlier “Unsupported pre-analysis migration version” error in Mendix 9 already indicated that the database was not fully compatible. In Mendix 10, that specific error is no longer thrown, but the client fails silently when it encounters incompatible metadata during UI initialization.
That’s why:
Between Mendix 9 and 10, the client lifecycle, metadata handling, and async data loading changed. If the existing database contains incompatible system or model metadata, the React client stops rendering parts of the UI without throwing visible errors.
Run the app with a fresh, empty database: