If you have enabled two-factor authentication (2FA) via an app such as Google Authenticator or via SMS, synchronization should be possible.
In this case, Powens will ask you for a confirmation code. Depending on the settings of your Degiro account, it may be:
generated by the app you used to set up 2FA, such as Google Authenticator (read Degiro help article)
sent to you by SMS
ℹ️ At Degiro, there is an alphanumeric password to enter your accounts via the website and a numeric-only password (therefore different) to enter them via the app. You will need to type the alphanumeric password used to enter via the website. The app password does not work to aggregate Degiro accounts on Finary.