The changes you make in Client Portal, such as column arrangements, dark/light theme, wide layout, etc., are saved on the browser cache memory on your computer and not on our back-end servers. Thus, you should be seeing the same columns and settings each time you login from the same computer and the same browser.
Some browsers (such as Firefox, Chrome, Edge, etc.) have a feature to clear cache and cookies when you exit. If this feature is activated on the browser, any changes you make in Client Portal will not be available the next time you login. Please check the settings on the browser and set them to allow the storage of cache, cookies and site settings (uncheck any settings which clears cache/cookies upon browser exit). This should then allow your browser to save the Client Portal settings successfully between sessions.
If for any reason you are still experiencing issues, you may also try using a different browser.