Do you see the message 'Action required' on Home with the button 'Get started' (app) or 'Start declaration' (web)? Then you still need to complete your DAC8 tax declaration. That button opens the declaration.
Tap or click it, enter your tax residence, your BSN or tax identification number and your date of birth, and choose 'Submit declaration'.
You can read more about DAC8 in the article 'DAC8: completing and changing your tax declaration'.